CBSE Class 8

Pollution of Air and Water Class 8 Extra Questions and Answers Science Chapter 18 PDF are solved by experts and will guide students in the right direction. Students can get how to tackle different questions easily by solving the Extra Questions for Class 8 Science Question bank on a regular basis.

Class 8 Science Chapter 18 Extra Questions and Answers Pollution of Air and Water

Extra Questions for Class 8 Science Chapter 18 Pollution of Air and Water with Answers

Pollution of Air and Water Class 8 Extra Questions Very Short Answer Type

Question 1.
Which monument in India is now one of the seven wonders of the world?
Answer:
It is Taj Mahal.

Question 2.
Why is the beauty of Taj Mahal threatened?
Answer:
Because of the air pollution in the area surrounding the Taj.

Question 3.
Name two sources of air pollutants.
Answer:
Factories and vehicles are the two prominent sources of air pollution.

Question 4.
Which gas is most responsible for global warming?
Answer:
C02 is most responsible for global warming.

Question 5.
Name the greenhouse gases.
Answer:
Carbon dioxide, methane, nitrous oxide, water vapour, etc. are called greenhouse gases.

Question 6.
Name the ambitious plan to save the river?
Answer:
It is called Ganga Action Plan.

Question 7.
What does untreated sewage thrown directly into rivers contain?
Answer:
Untreated sewage contains food- wastes, detergents and microorganisms.

Question 8.
What does water contaminated with sewage may contain?
Answer:
It contains bacteria, viruses, fungi and parasites.

Question 9.
What is potable water?
Answer:
Water which is suitable for drinking is called potable water.

Pollution of Air and Water Class 8 Extra Questions Short Answer Type 1

Question 1.
What is the impact of reducing quality of air and water on our lives?
Answer:
There is a great impact of reducing quality of air and water on our lives. The number of people suffering from various pollution-borne diseases is rising day by day.

Question 2.
State the constituents of air.
Answer:
Air consists of a mixture of gases. By volume about 78% of thik mixture is nitrogen and about 21% is oxygen. Carbon dioxide, argon, methane, ozone, water vapour are also present in very small quantity.

Question 3.
What is meant by air pollution?
Answer:
When the air is contaminated by unwanted substances which cause harmful effects on both the living and non-living components, it is referred to as air pollution.

Question 4.
What reduces visibility in air?
Answer:
Automobiles which burn diesel and petrol, produce tiny particles which remain suspended in air for long periods. They reduce visibility in air.

Question 5.
Are non-living things also affected by air pollution?
Answer:
Yes, the air pollution is affecting not only living beings, but also the non-living things. An example of this is discolouring the white marble of Taj Mahal due to air pollution. Similarly, many other buildings, monuments and statues are also getting affected.

Question 6.
Which industries are responsible for the yellowing of Taj in Agra?
Answer:
The industries located in and around Agra are rubber processing, automobiles, chemicals and especially the Mathura oil refinery have been responsible for the yellowing of Taj in Agra.

Question 7.
What are the reasons of water scarcity?
Answer:
Water is becoming scarce day by day due to increase in population, industries and agricultural activities.

Question 8.
How is water getting polluted?
Answer:
Whenever substances such as sewage, toxic chemicals, silt, etc., which are harmful to life, get mixed with water, the water becomes polluted.

Question 9.
What is the impact of putting chemical fertilizers in water?
Answer:
Putting chemical fertilizers in water leads to algae bloom, which increase toxicity of water. Again when they die, they are fed by decomposers like bacteria, which uses dissolved oxygen of water. Thus, survival of organism living in water become tough and they die out of stress.

Pollution of Air and Water Class 8 Extra Questions Short Answer Type 2

Question 1.
What is the thick fog-like layer in the atmosphere during winter? How is it formed?
Answer:
The thick fog like layer seen in the atmosphere especially in winter is smog. The smog is made up of smoke and fog. Oxides of nitrogen combine with other air pollutants and fog contributing to the formation of smog. It causes breathing difficulties such as asthma, cough and wheezing in children.

Question 2.
What are the directives of supreme court to control air pollution to save Taj?
Answer:
The supreme court has taken several steps to save the Taj Mahal from getting damaged by toxic chemicals.
(i) It has ordered the industries to switch to cleaner fuels like CNG (Compressed Natural Gas) and LPG (Liquefied Petroleum Gas).
(ii) The automobiles should switch to unleaded petrol in the Taj zone.

Question 3.
What are the impacts of global warming on atmosphere?
Answer:
Global warming can cause sea-levels to rise dramatically. In many places, coastal areas have already been flooded. Global warming could result in wide-ranging effects on rainfall patterns, agriculture, forests, plants and animals. It also brings about climatic changes. It may bring about the rise in temperature to more than two degrees Celsius, a level considered dangerous.

Question 4.
How does water becomes impure? How will you know that water is impure?
Answer:
Water becomes dirty after using it for washing clothes, bathing, etc. This means that we are adding such materials to water, which degrade its quality. These materials come from human sources, but, they could also be from natural sources. By the smell, colour, acidity and turbidity of the water we can know that water is impure.

Question 5.
How is Ganga one of the ten endangered rivers of the world?
Answer:
A study by the World Wide Fund for Nature found that Ganga is one of the ten endangered rivers in the world. It is because towns and cities, through which this river flows, dispose off large quantities of garbage, untreated sewage, dead bodies, and many other harmful things, directly into the river. In fact, the river is “dead” at many places where the pollution levels are so high that aquatic life cannot survive.

Question 6.
What is Ganga Action Plan? What is its aim?
Answer:
The Ganga Action Plan is an ambitious plan which was launched to save the river Ganga in 1985. It aims to reduce pollution levels by treating domestic sewage, building electric crematories and reducing industrial waste. Apart from this water treatment plant are installed for physical, chemical and biological treatment of water.

Question 7.
Radha saw her grandmother using oil and vinegar while preserving vegetables and fruits. Why oil and vinegar has been, used for preservation?
Answer:
Preservation by oil and vinegar: The layer of oil on “top of food prevents oxygen from entering the food. Some microbes do not survive in absence of oxygen. Some microbes cannot survive in acidic environment and thus vinegar is an effective food preservative.

Question 8.
Is hot water also a pollutant?
Answer:
Yes, hot water too is a pollutant. This is usually the water from power plants and industries that is released into the rivers. It can raise the temperature of the water bodies, in turn, depleting oxygen content, adversely affecting the aquatic animals and plants.

Pollution of Air and Water Class 8 Extra Questions Long Answer Type

Question 1.
What are the ways in which atmospheric air gets polluted? Discuss.
Answer:
The ways in which atmospheric air gets polluted are :

1. Many industries like petroleum refineries and automobile produce gaseous pollutants like sulphur dioxide and nitrogen dioxide.
2. Sulphur dioxide is produced by combustion of fuels like coal in power plants, which causes respiratory problems including permanent lung damage.
3. CFGs used in refineries, AC’s and aerosol sprays damage in ozone layer of atmosphere, which protect us from harmful UV rays of the Sun.
4. Automobile which burn diesel and petrol, produce tiny particles, that reduce visibility.
5. Industrial processes like steelmaking and mining involves such processes which release a lot of harmful gases, solid particles, dust, etc. which contribute in polluting air.

Question 2.
Describe greenhouse effect and its side effects as global warming.
Answer:
The sun rays that pass through the atmosphere, warms the earth’s surface. Apart of these radiation that falls on the earth is absorbed by it and a part is reflected back j into space. Some of the reflected radiations are trapped by the atmosphere and are not allowed to go out of the earth’s atmosphere.

These trapped radiations further warm the earth. This resembles a greenhouse in a nursery where sun’s heat is allowed to get in but is not allowed to go out. The trapped heat warms the greenhouse. The trapping of radiation by the earth’s atmosphere performs a similar function. That is why, it is called the greenhouse effect.

As a result of greenhouse effect, the average temperature of the earth’s atmosphere is gradually increasing. This is known as global warming.

Global warming has become a Serious threat to the survival of life on earth, because:
(i) It has already started melting the icebergs, due to which level of water in the sea has increased and many cities at coastal areas are threatened to be submerged completely.
(ii) It will too result in change in climate and rainfall pattern.

Question 3.
Differentiate between manure and fertilizers.
Answer:

Stars and the Solar System Class 8 Extra Questions and Answers Science Chapter 17 PDF are solved by experts and will guide students in the right direction. Students can get how to tackle different questions easily by solving the Extra Questions for Class 8 Science Question bank on a regular basis.

Class 8 Science Chapter 17 Extra Questions and Answers Stars and the Solar System

Extra Questions for Class 8 Science Chapter 17 Stars and the Solar System with Answers

Stars and the Solar System Class 8 Extra Questions Very Short Answer Type

Question 1.
What is the brightest object in the night sky?
Answer:
The moon is the brightest object in the night sky.

Question 2.
Moon revolves around, which celestial body?
Answer:
The moon revolves around the Earth.

Question 3.
Which celestial bodies revolve round the Sun?
Answer:
Planets along with their satellites, comets, asteroids.

Question 4.
When did man land on the moon for the first time?
Answer:
Man landed on the moon for the first time on July 21, 1969.

Question 5.
Who was the first human being to set foot on the moon?
Answer:
Neil Armstrong was the first human being to set foot on the moon.

Question 6.
Who was the second astronaut who landed on the moon after Neil Armstrong?
Answer:
Edwin Aldrin was the second astronaut who landed on the moon.

Question 7.
What is the speed of light in air?
Answer:
The speed of light in air is 3 × 105 km per second.

Question 8.
Which direction do stars move?
Answer:
Stars move from east to west.

Question 9.
Is there any change in the shape of the constellations?
Answer:
The shape of the constellations does not change.

Question 10.
What is the other name of Orion?
Answer:
The other name of the Orion is Hunter.

Question 11.
What does Cassiopeia look like?
Answer:
Cassiopeia looks like a distorted letter W or M.

Question 12.
Planets shine like stars. Do planets have light of their own?
Answer:
Although the planets shine like stars, but they do not have light of their own.

Question 13.
Do all planets have satellites ?
Answer:
Not all planets, but some of them have satellites.

Question 14.
Does Venus have moon ?
Answer:
Venus does not have moon or satellite of its own.

Question 15.
Name the only planet in the solar system which has life on its surface.
Answer:
The Earth is the only planet in the solar system where life is known to exist.

Question 16.
What is called equatorial plane of the Earth?
Answer:
The plane of the equator is called the equatorial plane of the Earth.

Question 17.
Which planet is the first outside from Earth (Orbit) in terms of distance from the Sun?
Answer:
It is Mars.

Question 18.
Compare the mass of Jupiter with that of Earth.
Answer:
Mars of Jupiter is about 318 times that of Earth.

Question 19.
Which is the largest planet of the solar system?
Answer:
The largest planet of the solar system is Jupiter.

Question 20.
Does Jupiter have rings?
Answer:
Yes, Jupiter has faint rings around it

Question 21.
Name the outermost planets of the solar system.
Answer:
Uranus and Neptune are the outermost planets of the solar system.

Question 22.
What is the other name of shooting star?
Answer:
The other name of the shooting star is meteor.

Stars and the Solar System Class 8 Extra Questions Short Answer Type 1

Question 1.
Why was the village sky so different from the night sky in big cities?
Answer:
Due to bright lights, smoke and other atmospheric pollution, a clear view of night sky in the big cities is rare, whereas it is possible in the village night sky.

Question 2.
What is meant by the term celestial object ? What is the brightest object in the night sky ?
Answer:
The stars, the planets, the moon and many other objects in the sky are called celestial objects. The moon is the brightest object in the night sky.

Question 3.
What is the full moon day ? What happens to the moon after full moon day ?
Answer:
The day on which the whole disc of the moon is visible is known as the full moon day. Thereafter, every night the size , of the bright part of the moon decreases.

Question 4.
What is new moon day and the crescent moon ? .
Answer:
On the fifteenth day after full moon day, the moon is not visible. This day is known as the new moon day.

The next day of new moon day, only a small part of the moon appears in the sky, which is called the crescent moon.

Question 5.
How many rotations are completed by the moon, when it completes one revolution?
Answer:
The moon completes one rotation on its axis as it completes one revolution around the Earth.

Question 6.
Why do stars appear to us like points, whereas Sun looks bigger?
Answer:
The stars are million times farther away than the Sun. That is why, the stars appear to us like points. On the other hand, The Sun is nearer to the Earth than other stars, so the Sun looks bigger.

Question 7.
How far is the Sun from the Earth? Which is the next star nearest to the Earth?
Answer:
The Sun is nearly 150,000,000 kilometres (150 million km) away from the Earth. The next nearest star to the Earth is the Alpha Centauri.

Question 8.
What is the distance of Alpha Centauri from Earth?
Answer:
The next nearest star to the Earth after the Sun is Alpha Centauri, which is at a distance of about 40,000,000,000,000 km from the Earth.

Question 9.
Does the Pole star move? Is it a star or a planet?
Answer:
The Pole star is not a planet. It is a star. The Pole star does not appear to move like other stars as it lies close to earth’s axis of rotation.

Question 10.
What is an orbit?
Answer:
A planet has a definite path in which it revolves around the Sun. This path is called an orbit.

Question 11.
What is the period of revolution? What happens if distance of a planet from the Sun increases?
Answer:
The time taken by a planet to complete one revolution is called its period of revolution. The period of revolution increases as the distance of the planet from the Sun increases.

Question 12.
What is the period of rotation?
Answer:
The time taken by the planet to complete one rotation is called its period pf rotation.

Question 13.
What is meant by the term satellite? What is moon?
Answer:
A body revolving around another body is called a satellite. Generally, we use the term satellite for the bodies revolving around a planet. Moon is the natural satellite of the Earth.

Question 14.
What do you understand by natural satellite?
Answer:
Any celestial body revolving around another celestial body is called its natural satellite.

Question 15.
What do you understand by artificial satellite?
Answer:
There are many man-made satellites revolving round the Earth. These are called artificial satellites of the Earth.

Question 16.
What is unusual in the rotation of Venus?
Answer:
The rotation of Venus on its axis is somewhat unusual. It rotates from east to west while the Earth rotates from west to east.

Question 17.
Why is Venus called a morning or an evening star?
Answer:
Sometimes Venus appears in the eastern sky before sunrise. Sometimes it appears in the western sky just after sunset. That is why, it is often called a morning or an evening star, although it is not a star.

Question 18.
How is Venus observed in the sky?
Answer:
Venus cannot be observed very high in the sky. It can be observed either 1-3 hours before sunrise’ or 1-3 hours after sunset.

Question 19.
Does Venus show phases like moon?
Answer:
If Venus is observed through a telescope, it shows phases just like the moon.

Question 20.
Why does the Earth appear blue-green from space ?
Answer:
From space, the Earth appears blue and green due to the reflection of light from water and land mass on its surface.

Question 21.
Is axis of rotation of the Earth perpendicular to the plane of its orbit? How does the change of seasons take place?
Answer:
The axis of rotation of the Earth is not perpendicular to the plane of its orbit. The change of seasons on the Earth is caused due to tilted axis of rotation of Earth.

Question 22.
What are equatorial and orbital planes of the Earth?
Answer:
The plane of the equator is called the equatorial plane of the Earth while the plane in which the Earth revolves round the Sun is called the orbital plane of the Earth.

Question 23.
Why is Mars called the red planet? How many natural satellites does Mars have?
Answer:
Mars appears slightly reddish and, therefore, it is also called the red planet. Mars has two small natural satellites.

Question 24.
Which planets are called inner planets?
Answer:
Mercury, Venus, Earth ajid Mars are much nearer to the Sun than the other planets. They are, therefore, called the inner or terrestrial planets.

Question 25.
(i) What is the angle (argument) between Earth’s equatorial of orbital plane?
(ii) What is the angle between earth’s axis and orbital plane ?
Answer:
(i) 23.5°
(ii) 66.5°

Stars and the Solar System Class 8 Extra Questions Short Answer Type 2

Question 1.
What is light year? Which is nearest star to the sun and how far away it is?
Answer:
Light year is the distance travelled by light in one year. Large distances in the space are measured in light year. The distance of the Sun from the Earth may be said to be about 8 light minutes. The nearest star to the sun is Alpha Centauri. The distance of Alpha Centauri is about 4.3 light years.

Question 2.
Write four uses of artificial satellites.
Answer:
Uses of artificial satellites:
(a) They help in television and radio transmission.
(b) They help in telephonic communication.
(c) They help to study and forecast the weather by sending cloud pictures to the Earth, taken from space.
(d) They help in locating mineral elements by remote sensing (collecting information from distance).
(e) They help the scientists, to explore the universe in a better way. (Any four)

Question 3.
Describe the Sun in brief.
Answer:
The Sun is the nearest star from us. It is continuously emitting huge amounts of heat and light. The Sun is the source of almost all energy on the Earth. In fact, the Sim is the main source of heat and light to all the planets that revolve around it.

Question 4.
How can you differentiate between planets and stars?
Answer:
The simplest method of identifying planets from stars is that stars twinkle whereas planets do not. Also, they (planets) appear to change their positions with respect to the stars. A planet has a definite path (orbit) to revolve around the Sun. The stars do not have orbits.

Question 5.
What is meant by outer planets? Describe.
Answer:
The planets outside the orbit of Mars, namely Jupiter, Saturn, Uranus and Neptune are much farther from the Sun than that the inner planets. So, they are called the outer planets. The masses and sizes of the outer planets are much larger than the masses and sizes of the inner planets. They have ring system around them. The outer planets have a large number of satellites.

Stars and the Solar System Class 8 Extra Questions Long Answer Type

Question 1.
Describe
(i) Asteroids
(ii) Comets
(iii) Meteors
(iv) Meteorites and
(iv) Meteor showers.
Answer:
(i) Asteroids: The large number of small objects that revolve around the Sun and occupy the large gaps between the orbits of Mars and Jupiter are called asteroids. These can be seen by large telescopes only.

(ii) Comets: They are also the members of our solar system. They revolve round the Sun in highly elliptical orbits. The period of their revolution round the Sun is very large.

The comet has a bright head with a long tail. The length of comet’s tail grows in size as it approaches the Sun. The tail of a comet is always directed away from the Sign. There are many comets which appear only after a definite time period. One of such comets is the Halley’s comet, which takes 76 years to reappear. It was last seen in 1986. The next time it will reappear in 2062.

(iii) Meteors: Bright streaks of light seen at night in the sky are called shooting stars or meteors. Meteors are usually small heavenly bodies which enters the Earth’s atmosphere with a very high speed, a friction is produced due to which the meteor heats up to such an extent that it burns out in a very short time. That is why the bright streak of light appears for a very short while.

(iv) Meteorites: Sometimes meteors are so large that a part of them reaches the surface of the Earth before they burn off completely. These are called meteorites. These help the scientists in investigating the nature of the material from which the solar system was formed.

(v) Meteor showers: When Earth crosses the tail of a comet, swarms of meteors are seen. These are known as meteor showers. Some meteor showers occur at regular times each year.

Question 2.
Write a brief note on the planet ‘Earth’.
Answer:
Earth is the only planet in the solar system where life is known to exist. Life exists on Earth because Earth is situated just at the right distance from the Sun. Certain environmental conditions are also responsible for the existence and continuation of life on the Earth. These include presence of water and suitable atmosphere, right temperature range, and a blanket of ozone.

From the space, the Earth appears blue-green due to the reflection of light from water and landmass on its surface. The axis of rotation of the Earth is not perpendicular to the plane of its orbit. The change in seasons on the Earth is caused, due to this tilt. The Earth has only one satellite, namely moon.

The equatorial plane and orbital plane of earth are inclined to each other at an angle of 23.5°. This means that the axis of the Earth is inclined to its orbital plane at and angle of 66.5°. So, the axis of the Earth makes an angle of 23.5° with the perpendicular to the orbital plane.

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NCERT Class 8 Social Science Extra Questions and Answers

NCERT Class 8 History Extra Questions

Extra Questions for Class 8 SST History: Our Pasts – III

1. How, When and Where Class 8 Extra Questions
2. From Trade to Territory Class 8 Extra Questions
3. Ruling the Countryside Class 8 Extra Questions
4. Tribals, Dikus and the Vision of a Golden Age Class 8 Extra Questions
5. When People Rebel Class 8 Extra Questions
6. Colonialism and the City Class 8 Extra Questions
7. Weavers, Iron Smelters and Factory Owners Class 8 Extra Questions
8. Civilising the Native, Educating the Nation Class 8 Extra Questions
9. Women, Caste and Reform Class 8 Extra Questions
10. The Changing World of Visual Arts Class 8 Extra Questions
11. The Making of the National Movement 1870s – 1947 Class 8 Extra Questions
12. India After Independence Class 8 Extra Questions

NCERT Class 8 Geography Extra Questions

Extra Questions for Class 8 SST Geography: Resources and Development

1. Resources Class 8 Extra Questions
2. Land, Soil, Water, Natural Vegetation and Wildlife Resources Class 8 Extra Questions
3. Mineral and Power Resources Class 8 Extra Questions
4. Agriculture Class 8 Extra Questions
5. Industries Class 8 Extra Questions
6. Human Resource Class 8 Extra Questions

NCERT Class 8 Civics Extra Questions

Extra Questions for Class 8 SST Civics: Social and Political Life – III

1. The Indian Constitution Class 8 Extra Questions
2. Understanding Secularism Class 8 Extra Questions
3. Why Do We Need a Parliament Class 8 Extra Questions
4. Understanding Laws Class 8 Extra Questions
5. Judiciary Class 8 Extra Questions
6. Understanding Our Criminal Justice System Class 8 Extra Questions
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8. Confronting Marginalisation Class 8 Extra Questions
9. Public Facilities Class 8 Extra Questions
10. Law and Social Justice Class 8 Extra Questions

Light Class 8 Extra Questions and Answers Science Chapter 16 PDF are solved by experts and will guide students in the right direction. Students can get how to tackle different questions easily by solving the Extra Questions for Class 8 Science Question bank on a regular basis.

Class 8 Science Chapter 16 Extra Questions and Answers Light

Extra Questions for Class 8 Science Chapter 16 Light with Answers

Light Class 8 Extra Questions Very Short Answer Type

Question 1.
What is virtual image?
Answer:
The image formed at a position behind the plane mirror is called a virtual image.

Question 2.
Can virtual image be obtained on a screen?
Answer:
No, virtual image cannot be obtained on a screen.

Question 3.
How many images, does one mirror form?
Answer:
The plane mirror can form only one image.

Question 4.
What name is given to the small opening behind the cornea?
Answer:
The name of the small opening behind the cornea is pupil.

Question 5.
Name the coloured part of the eye.
Answer:
The coloured part of the eye is called iris.

Question 6.
What is the function of iris ?
Answer:
It acts as a shutter or a diaphragm, controlling the size of pupil.

Question 7.
What part of eye contains several nerve cells?
Answer:
Retina contains several nerve cells.

Question 8.
Name two kinds of nerve cells found in retina.
Answer:
The two kinds of nerve cells are cones and rods.

Question 9.
What is the function of optic nerve and retina called ?
Answer:
This is called blind spot.

Question 10.
Who cart see very well in the night, but not during the day?
Answer:
Owl can see very well in the night but not during the day.

Question 11.
Which vitamin is found in green vegetables like spinach (palak)?
Answer:
Vitamin A.

Light Class 8 Extra Questions Short Answer Type 1

Question 1.
How can we see anything?
Answer:
The light when enters our eyes from an object, then we are able to see that object.

Question 2.
Define incident ray.
Answer:
The light ray, which strikes any surface, is called the incident ray.

Question 3.
Define reflected ray.
Answer:
The ray that gets bounced back from the polished surface is called the reflected ray.

Question 4.
What do you mean by laws of reflection ?
Answer:
There are two laws of reflection :
(i) The angle of incidence is equal to the angle of reflection.
(ii) The incident ray, reflected ray and the normal at the point of incidence all lie in the same plane.

Question 5.
Define plane.
Answer:
The flat surface with two-dimensional coordinates are termed as plane.

Question 6.
What do you mean by lateral inversion?
Answer:
When image is formed in a plane mirror, the left part appears as right and the right part appears as left. This phenomenon is known as lateral inversion.

Question 7.
Define regular reflection.
Answer:
The reflected rays are parallel to one another like the incident rays. This kind of reflection is called regular reflection. It takes place from a surface which is plane with no defects.

Question 8.
Define irregular or diffused reflection. How is it caused ?
Answer:
When all the reflected rays from a plane surface are not parallel like the incident rays, the reflection is known as irregular or diffused reflection.

Question 9.
Is diffused reflection due to the failure of the laws of reflection ? How is it caused ?
Answer:
No, the diffused reflection is not due to the failure of the laws of reflection. It is caused by irregularities in the reflecting surface.

Question 10.
Do we see objects due to reflected light ?
Answer:
Yes, everything except luminous object, we see around is seen due to reflected light. Moon, for example, receives light from the sun and reflects it. That is why we see the moon.

Question 11.
What is meant by luminous and illuminated objects ?
Answer:
The objects which have their own light, are called luminous objects, such as sun, fire, flame of candle, electric lamps, etc. The objects which reflect the light of other objects, are known as illuminated objects, such as moon.

Question 12.
Where are the periscopes used?
Answer:
The periscopes are used in submarines, tanks and by soldiers in bunkers to see things outside indirectly.

Question 13.
What happens if two plane mirrors in combination are used ?
Answer:
With a plane mirror, only one image of an object can be formed. But, if two mirrors in combination are used, then more than one image are formed.

Question 14.
What do you mean by dispersion of light? What is rainbow?
Answer:
The splitting of light by prism into seven constituent colours is known as dispersion of light. Rainbow is a natural example of dispersion of light.

Question 15.
What are two types of nerve cells ?
Answer:
There are two kinds of nerve cells:
(i) cones which are sensitive to bright light; and
(ii) rods which are sensitive to dim light. Cones send messages of colours also.

Question 16.
State the functions of eyelids.
Answer:
Eyelids protect eyes from any objects entering into the eye. Eyelids also shut when light is not required.

Question 17.
Describe the eyes of owls.
Answer:
The owl has a large cornea and a large pupil that allow more light in its eyes. Also, it has on its retina mostly rods and only a few cones.

Question 18.
What do you know about the cones and rods in the eyes of day birds?
Answer:
The day birds have more cones and a fewer rods, because cones are more sensitive to bright light and rods to dim light.

Question 19.
What is Braille?
Answer:
The most popular resource for visually challenged persons is Braille.

Light Class 8 Extra Questions Short Answer Type 2

Question 1.
What is kaleidoscope? What are its uses?
Answer:
The idea of number of images formed by mirrors placed at an angle to one another is used in an optical appliance called kaleidoscope. It is used to form numerous beautiful patterns. Designers of wall papers and fabric artists use kaleidoscope to get ideas for new patterns.

Question 2.
Describe the structure of eye.
Answer:
The eyes are one of the most important sense organs of human beings. Each eye has a roughly spherical shape. Outer tough coat of the eye is white that protects the interior of the eye from any damage. Its transparent front part is called cornea.

Behind the cornea, there is a small opening called the pupil. The size of the pupil is controlled by the iris which is the coloured part of the eye. This iris acts as a shutter or a diaphragm to control the amount of light entering into the eye. Behind the pupil is a lens which focuses light at the retina; placed at the back of eye.

Question 3.
What are the defects caused in eyes due to improper diet? How the defect is eradicated by taking particular type of food?
Answer:
If food is deficient in some components, eye may also suffer. Lack of vitamin A in our diet is responsible for many eye problems. Most common amongst them is night blindness.

One should, therefore, include in the diet components which have vitamin A. Raw . carrots, broccoli and green vegetables such as spinach (palak), methi, amarnath and cod liver oil are rich sources of vitamin A. Eggs, milk, curd, paneer, butter, ghee and fruits such as papaya, banana, mango, apple, dates, etc. also contain plenty of vitamin A.

Question 4.
Write a short note on persons which are visually handicapped.
Answer:
Some persons, including children, are visually handicapped. They have very limited vision to see things. Some persons cannot see at all since birth. Some persons lose their eyesight because of certain diseases.

Such persons, on their own try to identify things by touching, listening to the voices more carefully and bringing the things more closely to the eyes. In this way, they try to develop their senses more sharply. However, additional resources can further enable them to develop their capabilities.

Question 5.
Write the characteristics of image formed by a plane mirror.
Answer:
Characteristics of the image formed by plane mirror:
(a) The image formed by a plane mirror is virtual (imaginary) and erect.
(b) The image is laterally inverted. (The left side of object appear on right side of image.)
(c) The size of image is equal to that of object.
(d) The image formed is as far behind the mirror as the object is in front of it.

Question 6.
Draw a ray diagram to show the reflection produced by a plane mirror.
Answer:

Light Class 8 Extra Questions Long Answer Type

Question 1.
Describe the resources for the visually handicapped persons.
Answer:
Resources can be of two types :
(i) Non-optical aids, and
(ii) Optical aids.

(i) Non-optical aids include visual aids, tactual aids (using the sense of touch), auditory aids (using the sense of hearing) and electronic aids. With the help of visual aids, required size of words, suitable intensity of light and material at proper distances can be provided.

Tactual aids including Braille writer slate and stylus help the visually challenged persons in taking notes, reading and writing and in learning mathematics.

Auditory aids include cassette, tape recorders, talking books and other such programmes. Electronic aid such as talking calculators are also available for performing many computations. Closed-circuit television, also an electronic aid, enlarges printed materials with suitable contrasts and illumination.

Now-a-days, use of audio CDs and voice boxes with computers are also very helpful for listening and writing the desired text.

(ii) Optical aids include bifocal lenses, contact lenses, tinted lenses, other lens combinations, magnifiers and telescopic aids. While the lenses and their combinations are used to rectify visual limitations, telescopic aids are available to view chalk-boards and class demonstrations.

Question 2.
Describe in detail the Braille system of writing.
Answer:
Braille system has 63 dot patterns or characters. Each character represents a letter, combination of letters, common word or grammatical signs. Dots are arranged in cells of two vertical rows of three dots each. To identify the dpt patterns, dot positions are numbered 1, 2, 3 downwards on the left and 4, 5, 6 downward on the right as shown below :
1 ……….. 4
2 ……….. 5
3 ……….. 6

Use of the above notations:
Pattern of dots to represent English alpha-bets and some common words is shown below:

These dots when embossed on Braille sheet, help visually usually challenged to recognize words by touching. For the purpose, the words are slightly raised.

Hope the knowledge provided regarding the Light Class 8 Extra Questions and Answers has helped you to the possible extent. For more info feel free to reach us and we will guide you at the earliest possibility. Stay connected to our site to avail latest updates on Extra Questions for Various Classes instantly.

Some Natural Phenomena Class 8 Extra Questions and Answers Science Chapter 15 PDF are solved by experts and will guide students in the right direction. Students can get how to tackle different questions easily by solving the Extra Questions for Class 8 Science Question bank on a regular basis.

Class 8 Science Chapter 15 Extra Questions and Answers Some Natural Phenomena

Extra Questions for Class 8 Science Chapter 15 Some Natural Phenomena with Answers

Some Natural Phenomena Class 8 Extra Questions Very Short Answer Type

Question 1.
What happens when a charged balloon is brought close to another charged balloon?
Answer:
They repel each other.

Question 2.
Why does a charged eraser when brought close to another charged rubber, repel each other?
Answer:
Because similar charges repel each other.

Question 3.
What happens when a charged eraser is brought close to charged balloon and why?
Answer:
They would attract each other because opposite charges attract.

Question 4.
Why does a charged glass rod attract a charged plastic straw? Give reason.
Answer:
There are two opposite charges, therefore, they attract each other.

Question 5.
Are metals good conductors?
Answer:
Yes, all metals are good conductors.

Question 6.
Why do paper strips receive the same charge from the charged refill through the metallic needle?
Answer:
Because metals are good conductor of electricity. So, it contributes same charge to the paper strips through the metallic needle.

Question 7.
What happens when person touches the metallic wire of an electro¬scope after charging of foil strips ? Give reasons for your answer.
Answer:
When a person touches the metallic wire of an electroscope after charging its foil strips; the foil strips collapse. It happens so because the foil strips lose charge to the earth through human body which is a good conductor of electricity.

Question 8.
Is carrying umbrella during thunderstorm advisable? Why?
Answer:
No, carrying umbrella during the thunderstorm is not advisable, because lightning may strike on the person carrying the umbrella due to its pointed rod.

Question 9.
If one is in the forest, where should he take shelter during thunderstorm?
Answer:
The person should take shelter under the shortest trees around him.

Question 10.
During thunderstorm, which phone, should be used mobile phone, cordless phone or landline ?
Answer:
It is safe to use mobile phones and cordless phones.

Question 11.
Should one take bath during thunderstorm ?
Answer:
Bathing should be avoided during thunderstorm to avoid contact with running water. .

Question 12.
What would you do with T.V., computers, etc. during thunderstorm ?
Answer:
These should not be played, instead these should be unplugged.

Question 13.
What parts of human body are damaged by lightning ?
Answer:
Damage to nervous system, burn injuries, loss of hearing or sight, short-term memory loss, broken bones, etc., can occur due to lightning.

Question 14.
Can you predict the occurrence of earthquake ?
Answer:
No, prediction of earthquake is not possible.

Question 15.
When did the last major earthquake take place in India and where ?
Answer:
The last major earthquake in India occurred on 8th of October 2005 in Uri and Tangdhar towns of north Kashmir.

Question 16.
Is Richter a linear scale ?
Answer:
No, Richter scale is not a linear scale.

Question 17.
What is responsible for sparks in the sky ?
Answer:
Electricity is responsible for this phenomenon.

Question 18.
Which phenomenon is yet to be predicted?
Answer:
It is an earthquake.

Some Natural Phenomena Class 8 Extra Questions Short Answer Type 1

Question 1.
What was known to ancient Greeks about amber?
Answer:
The ancient Greeks knew as early as 600 BC that amber (a kind of resin), when rubbed with fur, attracted light objects such as hairs, twigs, etc.

Question 2.
If amber is rubbed for long enough, what happens as per Greeks ?
Answer:
As per Greeks when amber is rubbed for long enough, it could even generate a spark.

Question 3.
What happens when a plastic scale is rubbed on dry hair? Why?
Answer:
If plastic scale is rubbed on dry hair, the scale can attract very small pieces of paper because the scale develops charge on rubbing.

Question 4.
What happens when a plastic refill is rubbed with polythene ?
Answer:
When a plastic refill is rubbed with polythene, it acquires a small electric charge (negative).

Question 5.
How many types of charges are there ? What happens between two like charges and between two unlike charges if brought closer ?
Answer:
There are two types of charges – positive charges and negative charges. When two like charges are brought closer, they repel each other. When two unlike charges are brought closer to one another, they attract each other.

Question 6.
What type of charges are there on plastic straw and glass rod ?
Answer:
There is a negative charge on the plastic straw and is positive charge on glass rod. That is why, they attract one another.

Question 7.
What name is given to the electrical charge generated by rubbing ?
Answer:
The electrical charge generated by rubbing is called static electricity because these charges do not move.

Question 8.
What name is given to the electricity generated when charges move ?
Answer:
When the charges move from one conducting body to another, they generate electricity called current electricity.

Question 9.
What is meant by the term earthing? What is its advantage?
Answer:
The process of transfer of charges from a charged object to the earth is known as earthing. It is provided iri the electrical wiring in buildings to protect people from electrical shock due to any leakage of the electric current.

Question 10.
What happens during the development of a thunderstorm ?
Answer:
During the development of a thunderstorm, the air currents move upward while the v water droplets move downward. This vigorous movements cause separation of charges.

Question 11.
Which is the safest place during the lightning and thunderstorms ?
Answer:
A house or building is the safest place. If someone is travelling by a car or by bus, he/she is safe inside with windows and doors of the vehicle shut.

Question 12.
What are the destruction caused by the natural phenomena like thunderstorm, cyclone and lightning? Can these phenomena be predicted?
Answer:
These natural phenomena can cause large scale destruction of human life and property. Yes, these phenomena, fortunately, : can be predicted to some extent. The weather department can warn about a thunderstorm developing in some areas.

Question 13.
What is an earthquake? How does it take place?
Answer:
An earthquake is a sudden shaking or trembling of the earth. It is caused by a disturbance deep inside the earth’s crust.

Question 14.
What are seismic waves? Name the instrument that records these waves.
Answer:
The waves produced on the surface of the earth by tremors are called the seismic waves. These waves are recorded by an instrument called the Seismograph.

Question 15.
How is the power of an earthquake expressed ? What is the magnitude of destructive earthquake on this scale?
Answer:
The power of an earthquake is expressed in terms of magnitude on a scale called Richter scale. On this scale, the destructive earthquakes have magnitudes higher than 7.

Question 16.
Which areas in India are prone to earthquake?
Answer:
In India, Kashmir, western and Central Himalayas, the whole of North-East, Rann of Kachchh, Rajasthan and Indo-Gangetic, Plain are prone to earthquake. Some areas of south India also fall in the danger zone.

Some Natural Phenomena Class 8 Extra Questions Short Answer Type 2

Question 1.
If an earthquake is of magnitude in this scale. Would it cause much damage?
Answer:
No, it will not cause much damage. Destructive energy of an earthquake is measured on the Richter scale. The earthquake measuring 7 or more on Richter scale can cause severe damage to life and property.

Question 2.
What are the safety measures against lightning?
Answer:
During thunderstorm and lightning, no place outside is safe. That is why hearing a thunder we should rush to a safer place.

A house or a building is the safest place. If anybody is travelling by a car or bus, he/ she is safe inside with windows and doors of the vehicle shut.

Question 3.
Describe the meaning, use and construction of lightning conductor.
Answer:
Lightning conductor is a device used to protect tall building from the effect of lightning.
Construction: A metallic rod taller than the height of the building, is installed in the walls of the building during its construction. One end of the rod is kept out in the air and the other is fixed in the ground.
Use: Lightning rod provides easy route for transfer of electric discharge to the ground.
Precaution: It should not be touched during a thunderstorm.

Question 4.
If a thunderstorm occurs, what should you do ?
Answer:
If a thunderstorm occurs, there is always a possibility of lightning and cyclone accompanying it. So, it is better for us to take measures to protect ourselves from the damage caused by these events. Inside the house one should avoid using telephone, television, etc.

Bathing should be avoided during the thunderstorm to avoid contact with running water. Electrical appliances should be plugged off. If someone is outside, he/she should take shelter under shorter tree. When someone is in the open field, he/she should stay away from tall tree, electric poles, etc.

Question 5.
What are the damages caused by the earthquake? Name the place where some major earthquake occurred recently.
Answer:
Earthquake is a natural phenomenon, which we are not yet able to predict. It can cause damage to human life and property on a large scale. The earthquake can cause floods, landslides and tsunami.

The last major earthquake which occurred in India was on 8th October 2005 in Uri and Tangdhar towns of North Kashmir. Before that a major earthquake occurred on 26th January 2001 in Bhuj district of Gujarat.

Question 6.
What is weak zone or fault zone? Name some of these zones in India.
Answer:
Since earthquakes are caused by the movements of plates, the boundaries of the plates are the weak zones of fault zone, where earthquakes are more likely to occur. In India, the areas most threatened are Kashmir, Western and Central Himalayas, the whole of North-East, Rann of Kachchh, Rajasthan and the Indo-Gangetic Plain. Some areas of South India also fall in the danger zone.

Question 7.
What is a Richter scale? Is it linear? What are the magnitudes of earthquakes that can cause severe damage to life and properties?
Answer:
The power of an earthquake is expressed in terms of magnitudes on a scale called Richter scale. This scale is not linear. The earthquake of magnitude 7 or more is destructive and can cause severe damage to life and property.

Some Natural Phenomena Class 8 Extra Questions Long Answer Type

Question 1.
What are the suggestions that can be followed to protect buildings against earthquakes?
Answer:
Given below are the suggestions that can be followed to protect buildings against earthquakes :

1. The buildings should be so designed that they become ‘Quake Safe’. For this purpose, qualified architects and structural engineers should be consulted.
2. In highly seismic areas, the use of mud or timber is better than using heavy construction material. Roofs should be kept as light as possible. In case the structure falls, the damage will not be heavy.
3. Cupboards and shelves should be fixed to the walls, so that they do not fall easily.
4. Since some buildings may catch fire due to an earthquake, it is necessary that all buildings, especially tall buildings, have fire fighting equipment in working order.

Question 2.
What steps should be taken for protection if an earthquake strikes ?
Answer:
In the event that an earthquake does strike, the following steps should be taken for protection:
(A) At home:

1. One should take shelter under a table and stay there till shaking stops.
2. One should stay away from windows.
3. One should stay away from tall and heavy objects that may fall on him/her.
4. If anybody is in bed, he/she should not get up but protect his/her head with a pillow.

(B) Outdoors :

1. One should find out a clear spot away from buildings, trees and overhead powerlines and drop to the ground.
2. If anybody is in a car or a bus, he/she should not come out. Instead the driver should be asked to drive slowly to a clear spot and should not come out till the tremors stop.

Question 3.
What are the causes of earthquakes? Describe the major cause.
Answer:
Causes of earthquakes:
(i) Movement of the earth’s plates (major cause): The outermost layer of the earth is not in one piece. It is fragmented. Each fragment is called a plate. These plates are in continued motion. The boundaries of the plates are the weak zones, where earthquakes are more likely to occur due to sliding of one plate over or below the other. The weak zones are also known as seismic or fault zones.
(ii) Volcanic eruption.
(iii) Underground nuclear explosion.
(iv) When earth is hit by a meteor.

Question 4.
Describe some of the precautions which are intended to safeguard people’s life and property against lightning.
Answer:
Precautions which are intended to safeguard people’s life and property against lightning are:
A. Outside

1. Use of open vehicles like motorcycle, tractor etc. should be avoided.
2. Do not carry umbrella during thunderstorm.
3. If in a forest, take shelter under shorter trees.
4. If no shelter is available, we should stay far from tall trees, poles or other metal object. We should squat low to the ground.

B. Inside the house

1. During a thunderstorm, we should, avoid contact with telephone cords, electrical wires and metal pipes.
2. Bathing should be avoided during thunderstorms to avoid contact with running water.
3. Electrical appliances like computer, T.V., A.C., etc. should be unplugged. Electrical lights remaining on do not cause any harm.

Hope the knowledge provided regarding the Some Natural Phenomena Class 8 Extra Questions and Answers has helped you to the possible extent. For more info feel free to reach us and we will guide you at the earliest possibility. Stay connected to our site to avail latest updates on Extra Questions for Various Classes instantly.

Chemical Effects of Electric Current Class 8 Extra Questions and Answers Science Chapter 14 PDF are solved by experts and will guide students in the right direction. Students can get how to tackle different questions easily by solving the Extra Questions for Class 8 Science Question bank on a regular basis.

Class 8 Science Chapter 14 Extra Questions and Answers Chemical Effects of Electric Current

Extra Questions for Class 8 Science Chapter 14 Chemical Effects of Electric Current with Answers

Chemical Effects of Electric Current Class 8 Extra Questions Very Short Answer Type

Question 1.
Most liquids which conduct electricity are solutions of _________ and __________.
Answer:
salt, water

Question 2.
Do some liquids also conduct electricity?
Answer:
Yes, some liquids also conduct electricity, e.g., mercury (metal), impure water, aqueous solution of acids, bases, etc.

Question 3.
When current flows in a wire, a compass needle kept nearby gets deflected. What effect of current is this?
Answer:
This is magnetic effect of current.

Question 4.
Is air an insulator under all conditions?
Answer:
Only dry air is an insulator, but damp air is a conductor.

Question 5.
Is salt solution a conductor?
Answer:
Yes, it is.

Question 6.
Can there be made a coating of one metal on another?
Answer:
Yes, by electroplating, it can be done.

Question 7.
In electroplating, what effect of current is observed?
Answer:
Chemical effect.

Question 8.
In electroplating of copper, a layer of copper builds upon the plate. But, what about the loses of copper from the solution?
Answer:
From the other electrode, an equal amount of copper gets dissolved in the solution.

Question 9.
Why chromium is electroplated on other inferior material?
Answer:
Because it has shiny appearance, it does not corrode and resists scratches as well.

Question 10.
Though silver and gold jewellery is expensive, we can get ornaments in the market which have the appearance of silver or gold at much less prices. How is this possible?
Answer:
Jewellery makers electroplate silver and gold on less expensive metals. These ornaments have the appearance of silver or gold but are much less expensive.

Chemical Effects of Electric Current Class 8 Extra Questions Short Answer Type 1

Question 1.
Define conductors.
Answer:
Materials which allow electric current to pass through them are called conductors, e.g., aluminium, copper, etc.

Question 2.
Define insulators.
Answer:
Materials, which do not allow electric current to pass through them are known as insulators or non-conductor, e.g., rubber, plastic, wood, paper, etc.

Question 3.
Do liquids also conduct electricity?
Answer:
Yes, some liquids also conduct electricity. But, all liquids do not conduct electricity, e.g., Tap water can conduct electricity, but distilled water cannot.

Question 4.
What precaution is taken in regard of the cell, while checking the tester? Why?
Answer:
While checking the tester, one must not join its free ends for more than a few seconds. Otherwise the cells of the battery will drain very quickly.

Question 5.
Sometimes even though the liquid allows the electric current to pass and the circuit is complete, bulb does not glow. What can be the reason?
Answer:
If the current through the circuit is too small, the filament of the bulb does not get heated to high temperature and it does not glow.

Question 6.
Why is tap water, a conductor of electricity?
Answer:
Tap water contains lots of mineral salts dissolved in it which make this water conductor of electricity.

Question 7.
Why is distilled water an insulator of electricity?
Answer:
Distilled water is free from impurities like salts, minerals, dust, etc., so it is an insulator of electricity.

Question 8.
What precaution should be applied while you handle an electrical appliance?
Answer:
We should never handle electrical appliances with wet hands or while standing on a wet floor, because electricity can conduct through the water and there could be an electrocution.

Question 9.
What can be done to make water more conductive?
Answer:
A teaspoon of salt or a few drops of lemon juice (acid) can be added into the water, to make it more conductive.

Question 10.
What is meant by the term electroplating?
Answer:
The process of depositing a layer of any desired metal on another metallic object by means of electricity is called electroplating.

Question 11.
Why is zinc plated on to iron?
Answer:
Zinc is plated on to iron to protect it from corrosion and formation of rust.

Chemical Effects of Electric Current Class 8 Extra Questions Short Answer Type 2

Question 1.
Explain the working of a lightning conductor.
Answer:
Lightning conductor is a safety device that protects a tall .building from lightning strike, by providing an easy and alternative path to the heavy charge of lightning. It consists of a long metal rod fixed with side wall of tall building such that its upper end like trishul much above the building while lower end runs deep under earth and joins a large metal plate. Whenever there is lightning, the heavy charge of the lightning is conducted through the metal rod to the earth and the building remains safe.

Question 2.
What happens at the electrodes connected to the terminals of a battery, when the electrodes are immersed in water and current is passed through the electric circuit?
Answer:
Electrolysis of water takes place and bubbles of oxygen and hydrogen are produced. Oxygen bubbles are formed at positive electrode and hydrogen bubbles are formed at negative electrode.

Question 3.
What happens when an electric current is passed through the conducting solution?
Answer:
The passage of an electric current through a conducting solution causes chemical reactions. As a result, bubbles of gas may be formed, deposits of metal on electrodes may be seen and changes of colour of solution may occur, depending on what solutions and electrodes are used. This is called the chemical effects of the electric current.

Question 4.
Why is disposal of the used conducting solution in the electroplating factories a major concern?
Answer:
In the electroplating factories, the used conducting solution is a hazardous waste which creates a lot of pollution. That is why, the disposal of the used conducting solution is a major concern.

Question 5.
How is copper sulphate solution electrolysed? What are the outcome of this chemical change?
Answer:
When electrical current is passed through the copper sulphate solution, copper sulphate dissociates into copper and sulphate.

The free copper gets drawn to the plate connected to the negative terminal of the battery and thus gets deposited on that plate. From the other plate an equal amount of copper gets dissolved in the solution. This means that copper gets transferred from one plate to another.

Question 6.
What is the benefit of chromium plating on another cheaper materials?
Answer:
Chromium has a shiny appearance. It does not corrode and resists scratches. However, chromium is expensive and it cannot be used to make the whole object. So, the object is made from a cheaper metal and only a coating of chromium over it is done.

Question 7.
How are tin cans made of? Why are tin cans used for storing food items?
Answer:
Tin cans used for storing food items, are made of by electroplating a layer of tin on to iron. The tin is less reactive as compared to iron. Thus, the food is protected against spoilage.

Chemical Effects of Electric Current Class 8 Extra Questions Long Answer Type

Question 1.
(a) Mention two uses of electroplating.
(b) Explain what happens when electric current is passed through two copper electrodes dipped in copper sulphate solution.
Answer:
(a) (i) Chromium plating is done on various objects like car parts, wheel rims, bath taps, etc.
(ii) Plating of silver or gold is done on less expensive metals by jewellers.
(iii) Iron parts in bridges and automobiles are plated with zinc.
(iv) Tin cans for storing food are made by electroplating tin onto iron. (Any two)

(b) If we pass current through copper sulphate solution with two copper electrodes, copper from anode gets deposited on the copper plate connected to the negative terminal of the battery (Cathode). This is the technique used for the purification of copper.

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