CBSE Student can find here CBSE Class 10 Physics Human Eye Important Questions and Answers (Multiple Choice Question & Short Questions) by subject experts so that Candidates are well prepared with all major questions that can be asked in CBSE Class 10 Science board examination 2022-23 Check Now.
MULTIPLE CHOICE QUESTIONS
1. Colour of sky appears blue, due to the
(A) atmospheric refraction
(B) presence of plants in water
(C) scattering of light
(D) none of these
Ans: (C) scattering of light
2. Twinkling of stars is due to
(a) Reflection of light by clouds
(b) scattering of light by dust particles
(c) dispersion of light by water drops
(d) atmospheric refraction of starlight
Ans: (d) atmospheric refraction of starlight
3. Red colour is used as danger sign as
(A) red colour scattered least by smoke
(B) red colour scattered most by smoke
(C) Red colour absorbs by the smoke
(D) red colour moves fast in air
Ans: (A) red colour scattered least by smoke
4. The scattering of light by colloidal particles is called
(a) Tyndall effect
(c) atmospheric refraction
(d) internal reflection
Ans: (a) Tyndall effect
5. Which colour of light refracts most when passes through a prism-
Ans: (D) indigo
6. Which of the following controls the amount of light entering the eye
Ans: (B) iris
7. When white light passes through a prism, the component colour which Undergoes maximum bending is
Ans: (c) violet
8. The change of focal length of eye lens is caused by the action of the
(A) ciliary muscles
Ans: (A) ciliary muscles
9. Sunlight is passed through a transparent medium having very fine particles These particles scatter light.Which among the given components of light undergoes more scattering?
Ans: (d) blue
10 The least distance of distinct vision for a young adult with normal vision is about
(a) 25 m
(b) 2.5 cm
(c) 25 cm
(d) 2.5 m
Ans: (c) 25 cm
SHORT ANSWER QUESTIONS
1. What is colour-blindness? What kind of retinal cells are lacking in a person suffering from this defect?
Answer: The defect of the eye due to which a person is unable to distinguish between certain colours, is known as colour blindness. Cone-shaped retinal cells are responsible for making a person differentiate between colours. The colour blindpersons do not possess cone cells that respond to certain colours.
2. What happens to the image distance in the eye when we increase the distance of an object from the eye ?
Answer: The eye lens of a normal eye forms the images of objects at various distances on the same retina. Therefore, the image distance in the eye remains the same.
3. Explain why the planets do not twinkle?
Answer: The planets are much nearer to the earth than stars and because of this they can be considered as large source of light. If a planet is considered to be a collection of a very large number of point sources of light, then the average value of change in the amount of light entering the eye from all point size light sources is zero. Due to this the effect of twinkling is nullified.
4. Why is a normal eye not able to see clearly the objects placed closer than 25 cm?
Ans: A normal eye is unable to clearly see objects placed closer than 25 cm because the ciliary muscles of eyes are unable to contract beyond a certain limit. If the object is placed at a distance less than 25 cm from the eye, then the object appears blurred and produces strain in the eyes.
5. Why do stars twinkle?
Answer: Stars appear to twinkle due to atmospheric refraction. The light of a star after the entry of light in earth’s atmosphere undergoes refraction continuously till it reaches the surface of the earth. Stars are far away. So, they are the point source of light. As the path of light coming from stars keeps changing, thus the apparent position of stars keeps changing and the amount of light from stars entering the eye keeps twinkling. Due to which a star sometimes appears bright and sometimes dim, which is the effect of twinkling.
6. Why does the sky appear dark instead of blue to an astronaut?
Answer: As an astronaut moves away from the atmosphere of earth, the atmosphere becomes thin. Due to the absence of molecules (or dust particles) in air, the scattering of light does not take place. Thus, the sky appears dark in the absence of scattering.
7. Why does the sun appear reddish early in the morning?
Answer: The light coming from the sun passes through various denser layers of air in the earth’s atmosphere before reaching our eyes near the horizon. Most of the part of blue light and light of small wavelength gets scattered by dust particles near the horizon. So, the light reaching our eyes is of large wavelength. Due to this the sun appears reddish at the time of sunrise and sunset.