Human Eye and Colourful World Class 10 MCQ Questions With Answers
Question 1.
Study the following ray diagram :
In this diagram, the angle of incidence, the angle of emergence and the angle of deviation respectively have been represented by
(A) y, p and z
(B) x, q and z
(C) p, y and z
(D) p, z and y
Answer:
(C) p, y and z
Explanation:
Angle p is the angle of incidence as this angle is formed between the incident ray and the normal. Angle y is angle of emergence as it is formed between emergent ray and the normal, and angle z is the angle of deviation as it is formed between the emergent ray and the incident ray. Hence, the correct answer is p, y, z.
Question 2.
Which of the following phenomena of light are involved in the formation of a rainbow?
(A) Reflection, refraction and dispersion
(B) Refraction, dispersion and total internal reflection
(C) Refraction, dispersion and internal reflection
(D) Dispersion, scattering and total internal reflection
Answer:
(C) Refraction, dispersion and internal reflection
Explanation:
Dispersion means white light getting segregated into its component colours. Refraction bends the incident light to an angle that causes internal reflection and finally rainbow is formed.
Question 3.
Twinkling of stars is due to atmospheric
(A) dispersion of light by water droplets
(B) refraction of light by different layers of varying refractive indices
(C) scattering of light by dust particles
(D) internal reflection of light by clouds
Answer:
(B) refraction of light by different layers of varying refractive indices
Explanation:
Due to refraction of light by different layers of varying refractive indices, the apparent position of source of light keeps on changing. So stars appear to twinkle.
Question 4.
At noon the sun appears white as
(A) light is least scattered.
(B) all the colours of the white light are scattered awav.
(C) blue colour is scattered the most.
(D) red colour is scattered the most.
Answer:
(A) light is least scattered.
Explanation:
Sun is directly over the head and sunlight travel relatively shorter distance causing only little of the blue and violet colours to be scattered.
Question 5.
The clear sky appears blue because
(A) blue light gets absorbed in the atmosphere
(B) ultraviolet radiations are absorbed in the atmosphere
(C) violet and blue lights get scattered more than light of all other colours by the atmosphere
(D) light of all other colours is scattered more than the violet and blue colour light by the atmosphere
Answer:
(C) violet and blue lights get scattered more than light of all other colours by the atmosphere
Explanation:
A clear cloudless day-time sky is blue because molecules in the air scatter blue light from the sun more than they scatter red light. Rayleigh scattering is inversely proportional to the fourth power of wavelength, so that shorter wavelength violet and blue light will scatter more than the longer wavelengths (yellow and especially red light).
Question 6.
Which of the following statements is correct regarding the propagation of light of different colours of white light in air?
(A) Red light moves fastest
(B) Blue light moves faster than green light
(C) All the colours of the white light move with the same speed
(D) Yellow light moves with the mean speed as that of the red and the violet light
Answer:
(C) All the colours of the white light move with the same speed
Explanation:
Speed of light is a constant value regardless of its colour.
Question 7.
Which of the following phenomena contributes significantly to the reddish appearance of the sun at sunrise or sunset?
(A) Dispersion of light
(B) Scattering of light
(C) Total internal reflection of light
(D) Reflection of light from the earth
Answer:
(B) Scattering of light
Explanation:
Red colour scatters the least so that it travels the farthest. During sunset or sunrise, light has to travel a longer distance to reach us. Hence, only red light reaches to us and the sky appears reddish.
Question 8.
In an experiment to trace the path of a ray of light through a triangular glass prism, a student would observe that the emergent ray
(A) is parallel to the incident ray.
(B) is along the same direction of incident ray.
(C) gets deviated and bends towards the thinner part of the prism.
(D) gets deviated and bends towards the thicker part (base) of the prism.
Answer:
(D) gets deviated and bends towards the thicker part (base) of the prism.
Explanation:
As ray emerges out of the prism, it moves from a denser to a rarer medium, and therefore, bends away from the normal. So, bends towards the thicker part (base) of the prism.
Question 9.
Study the following figure in which a student has marked the angle of incidence (∠i), angle of refraction (∠r), angle of emergence (∠e), angle of prism (∠A) and the angle of deviation (∠D). The correctly marked angles are:
Answer:
(A) ∠A and ∠i
(B) ∠A, ∠i and ∠r
(C) ∠A, ∠i, ∠e and ∠d
(D) ∠A, ∠i, ∠r and ∠d
Explanation:
The correctly marked angles are of ∠A and ∠i.
Assertion and Reason Based MCQs
Directions : In the following questions, A statement of Assertion (A) is followed by a statement of Reason (R). Mark the correct choice as.
(A) Both A and R are true and R is the correct explanation of A.
(B) Both A and R are true but R is NOT the correct explanation of A.
(C) A is true but R is false.
(D) A is false and R is true.
Question 1.
Assertion (A): A white light on passing through prism splits into its component colours as such that the red light emerges nearest to the base of the prism.
Reason (R): Wavelength of red light is more than other component colours and hence, red light deviates least.
Answer:
(D) A is false and R is true.
Explanation:
Dispersion takes place because the refractive index of medium for different wavelengths (colours) is different. The refractive index is inversely proportional to X Since kred is more than other colours wavelength. So, deviation is least for red and it appears farthest from the base of the prism.
Question 2.
Assertion (A): Sunlight reaches us without dispersion in the form of white light and not as its components.
Reason (R): Dispersion takes place due to variation of refractive index for different wavelength but in vacuum the speed of light is independent of wavelength and hence vacuum is a non-dispersive medium.
Answer:
(A) Both A and R are true and R is the correct explanation of A.
Explanation:
In vacuum speed of light is independent of wavelength. Hence, no dispersion takes places in vacuum. Thus, vacuum is a non-dispersive medium in which all colours travel with the same speed.
Question 3.
Assertion (A): In case of rainbow, light at the inner surface of the water drop gets internally reflected.
Reason (R): The angle between the refracted ray and normal to the drop surface is greater than the critical angle.
Answer:
(A) Both A and R are true and R is the correct explanation of A.
Explanation:
The rainbow is formed when light at the inner surface of the water drop gets internally reflected. If the angle between the refracted ray and normal to the drop surface is greater than the critical angle.
Question 4.
Assertion (A): Scattering of light is the reflection of light from an object in all directions.
Reason (R): The colour of scattered light depends on the size of scattering particles and wavelength of light.
Answer:
(B) Both A and R are true but R is NOT the correct explanation of A.
Explanation:
The reflection of light from an object in all direction is called scattering of light. The colour of scattered light depends on the size of scattering particles and wavelength of light. Very fine particles scatter mainly blue light while particles of larger size scatter light of longer wavelength i.e. red light. If the size of the scattering particles is large enough, then the scattered light may even appear white.
Case-Based MCQs
Attempt any 4 sub-parts from each question. Each sub-part carries 1 mark.
I. A narrow beam of white light is passing through a glass prism as shown in the diagram. Study the diagram and answer any four questions from Question 1. to Question 5.
Question 1.
The phenomenon observed in above set-up is
(A) scattering of light
(B) dispersion of light
(C) reflection of light
(D) refraction of light
Answer:
(B) dispersion of light
Explanation:
The phenomenon of splitting of white light into its constituent colours after passing through a prism is called as dispersion of light. When the light enters the prism, all the colours have different speeds due to which its gets split into bands.
Question 2.
In nature, this phenomenon is observed in
(A) Formation of rainbow
(B) Twinkling of stars
(C) Blue colour of sky
(D) Advance sunrise
Answer:
(A) Formation of rainbow
Explanation:
Rainbow is caused by dispersion of sunlight by tiny water droplets present in the atmosphere which is one of the application of dispersion of light.
Question 3.
Which of the following statement is correct about constituents of white light based on above observations?
(A) White light consists of seven colours.
(B) Violet colour suffers minimum deviation.
(C) Red light suffers maximum deviation.
(D) All the colours of the white light move with different speed in vacuum.
Answer:
(A) White light consists of seven colours.
Explanation:
When the light disperses, various bands of light are clearly visible. It is clear from the figure that the violet light suffers maximum deviation and red light suffers minimum deviation .All the colours of the white light move with the same speed in air or vacuum but with different wavelengths and frequencies.
Question 4.
The cause of dispersion of light is
(A) All the colors of light travel with the speed more than the speed of light.
(B) All the colors have different angles of deviation.
(C) All the colors do not travel with the same speed of light.
(D) All the colors have the same wavelength .
Answer:
(C) All the colors do not travel with the same speed of light.
Explanation:
The various colours of white light have different extent of refraction in a medium, All of colours of light do not travel with same speed in the medium which is the cause of dispersion of light.
Question 5.
Read the following statements carefully
(i) The prism behaves same as that of rectangular glass slab.
(ii) All the colours have different angles of deviation in case of dispersion through prism.
(iii) All the colours travel with the same speed of light in glass.
(iv) Dispersion of light is observed in case of rectangular glass slab.
Question 6.
Which of the above statements is true?
(A) Only (ii)
(B) (i) and (ii) only
(C) (i), (ii) and (iv) only
(D) All of the above
Answer:
(A) Only (ii)
Explanation:
A prism is made up of glass in which the faces are joined at a certain angle but in case of rectangular glass slab, the opposite faces are parallel to each other. As the light enters in the prism, all the colours travel with the different speed of light because glass is a denser medium as compared to air and dispersion of light is not observed in case of a rectangular glass slab. So, both prism and rectangular glass slab behave differently.