Find below the NCERT Exemplar problems and their solutions for Class 10 Science Chapter, Human Eye and Colourful World:

Multiple Choice Questions

Question 1. A person cannot see distinctly objects kept beyond 2 m. This defect can be corrected by using a lens of power

(a) +0.5 D

(b) ─0.5 D

(c) +0.2 D

(d) ─0.2 D

Answer. (b)

Explanation:  As the person with myopia uses a concave lens.

Question 2.  A student sitting on the last bench can read the letters written on the blackboard but is not able to read the letters written in his text book. Which of the following statements is correct?

(a) The near point of his eyes has receded away

(b) The near point of his eyes has come closer to him

(c) The far point of his eyes has come closer to him

(d) The far point of his eyes has receded away

Answer. (a)

Explanation: The student is suffering from hypermetropia wherein distant images are clear but the nearby images are blurry.

Question 3. A prism ABC (with BC as base) is placed in different orientations. A narrow beam of white light is incident on the prism as shown in figure. In which of the following cases, after dispersion, the third colour from the top corresponds to the colour of the sky?

Answer. (ii)

Explanation:  Inverted position of prism (II) gives the same color at third top as that of sky.

Question 4. At noon the sun appears white as

(a) light is least scattered

(b) all the colours of the white light are scattered away

(c) blue colour is scattered the most

(d) red colour is scattered the most

Answer. (a)

Explanation:  Sun is directly over head and sunlight travel relatively shorter distance causing only little of the blue and violet colours to be scattered.

Question 5. 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)

Explanation:  When Sunlight falls on tiny water droplets, rainbow is formed by dispersion, refraction and internal reflection of sunlight.

Question 6. 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)

Explanation:  The twinkling of a star is due to atmospheric refraction of light of stars.

Question 7. 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 lights of all other colours by the atmosphere

(d) light of all other colours is scattered more than the violet and blue colour lights by the atmosphere

Answer. (c)

Explanation:  The molecules in the air scatter blue light more than red light.

Question 8. 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)

Explanation:   Speed of light is a constant value regardless of its color.

Question 9. The danger signals installed at the top of tall buildings are red in colour. These can be easily seen from a distance because among all other colours, the red light

(a) is scattered the most by smoke or fog

(b) is scattered the least by smoke or fog

(c) is absorbed the most by smoke or fog

(d) moves fastest in air

Answer. (b)

Explanation:  Red colour is scattered the least by smoke or fog due to its largest wavelength.

Question 10. 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)

Explanation:  Red colour is scattered the least by due to its largest wavelength.

Question 11. The bluish colour of water in deep sea is due to

(a) the presence of algae and other plants found in water

(b) reflection of sky in water

(c) scattering of light

(d) absorption of light by the sea

Answer. (c)

Explanation: The fine particles in water scatter mainly blue light having shortest wavelength.

Question 12. When light rays enter the eye, most of the refraction occurs at the

(a) crystalline lens

(b) outer surface of the cornea

(c) iris

(d) pupil

Answer. (b)

Explanation: The transparent, anterior portion of outer layer of eyeball is termed as cornea which causes most of the bending of incident light rays, i.e. refraction, to make them converge which in turn causes image formation on retina.

Question 13. The focal length of the eye lens increases when eye muscles

(a) are relaxed and lens becomes thinner

(b) contract and lens becomes thicker

(c) are relaxed and lens becomes thicker

(d) contract and lens becomes thinner

Answer. (a)

Explanation: The focal length of the eye lens increases when eye muscles relaxed and becomes thinner.

Question 14. Which of the following statements is correct?

(a) A person with myopia can see distant objects clearly

(b) A person with hypermetropia can see nearby objects clearly

(c) A person with myopia can see nearby objects clearly

(d) A person with hypermetropia cannot see distant objects clearly

Answer. (c)

Explanation: Nearsightedness, or myopia is inability to see the far located objects clearly.