CBSE Class 10 Science Chapter-11 Human Eye and Colourful World – Free PDF Download
Free PDF download of Important Questions with Answers for CBSE Class 10 Science Chapter 11 – Human Eye and Colourful World prepared by expert Science teachers from latest edition of CBSE(NCERT) books only by CoolGyan to score more marks in CBSE board examination.
CBSE Class 10 Science Chapter-11 Human Eye and Colourful World Important Questions
CBSE Class 10 science Important Questions Chapter 11 – Human Eye and Colourful World
2 Mark Questions
1. The far point of a myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to correct the problem.
Ans. 
2. Draw a diagram to show the dispersion of white light by a glass prism.
Ans.
3. Name the phenomenon responsible for the observed twinkling of stars. Will this twinkling be observed by an observer on the moon.
Ans. Atmospheric refraction is responsible for twinkling of stars.
The observer on the moon will not observe twinkling of stars as moon has no atmosphere.
4. Name the part of the eye that
(a) determines the colour of a person’s eye
(b) Controls the amount of light entering the eye
Ans. (a) Cones cell present in retina
(b) Iris
5. What is the role of the ciliary muscles?
Ans. The ciliary muscles holds the eye lens in its position and when the muscles contract and relax it changes the shape of the eye lens which is turn increases or decreases the focal length of the eye lens
6. Which convex lens is called as converging lens?
Ans. A convex lens is called as a converging lens because it focuses all the parallel beam of light at its focus.
7. State the role of eye lens in the human eye?
Ans. If focuses the light says entering the eye to form a real and inverted image of the object on the retina.
8. What is meant by power of accommodation of eye?
Ans. The ability of the eye lens to adjust its focal length, so as to clearly focus rays coming from distant as well as near objects on the retina, is called the power of accommodation of the eye.
9. A person with a myopic eye cannot see objects beyond 1.2 m distinctly. What should be the corrective lens used to restore proper vision?
Ans. A person with a myopic eye should use a concave lens of focal length 1.2 m so as to restore proper vision.
10. What is the far point and near point of the human eye with normal vision?
Ans. For a human eye with normal vision the far point is at infinity and the near point is at 25 cm from the eye.
11. A student has difficulty reading the blackboard while sitting in the last row. What could be the defect the child is suffering from? How can it be corrected?
Ans. The student is suffering from myopia or short sightedness. The defect can be corrected by the use of concave lens of suitable power.
12. The far point of a myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to correct the problem?
Ans. To correct the myopia the person concerned should use concave lens of focal length (f) = -80 cm = -0.80 m Power of lens (P) = 1/f(m) = 1/-0.80 = 100/-80 = -1.25 D.
13. Why is a normal eye not able to see clearly the objects placed closer than 25 cm?
Ans. Due to limit of power of accommodation, the focal length of the eye lens cannot be decreased below certain minimum limit. So, a normal eye cannot see clearly the objects placed closer than minimum distance, called near point of the eye.
14. What happen to the image distance in the eye when we increase the distance of an object from the eye?
Ans. The image is formed on the retina even on increasing the distance of an object from the eye. In fact, the eye lens becomes thinner and its focal length increases as the object is moved away from the eye and consequently image is formed on the retina.
15. Why does the Sun appear reddish early in the morning?
Ans. In early morning, the Sun is situated near horizon. Light from the Sun passes through thicker layers of air and covers a larger distance in earth’s atmosphere before reaching our eyes. While passing through atmosphere blue light is mostly scattered away and the Sun appear reddish.
16. A person wears eye glass of focal length 70 cm what is the far point of the person?
Ans. l/f=l/v-l/u
V=?
F=-70 cm
1/v=1/-70 v=-70 cm
17. If your eye glasses have focal length 60 cm what is your nor point?
Ans. l/f=l/v-l/u
1/60=l/v+1/25
v=-43 cm.
18. Why do we observe random wavering or flicking of the objects near a fire or on a very hot day?
Ans. Area above the fire is hot, and its density and hence refractive index changes frequently. Therefore, apparent image of the object also changes.
19. Why are we not able to see the things clearly when we come out of a darkroom?
Ans. When we are in dark, pupil size is bigger. As we come out of dark room, its size needs to Become smaller. For that time-interval person is unable to see.
20. What is the function of optic nerve in human eye?
Ans. Optic nerve carries the image formed on the retina to the brain in the form of electrical signals.
21. Why do different colours deviate though different angles on passing through a prism?
Ans. This is because different colours travel through glass with different speeds and glass has different refractive index for different colours.
22. Name the defect of vision in person
a. Whose near point is more than 25 cm away’?
b. Whose far point is less than infinity.
Ans. a. Hypermetropia
b. Myopia
23. What is a spectrum?
Ans. The band of seven colours obtained by dispersion of white light is called spectrum.
24. Why does clear sky look blue?
Ans. The sky appears blue because the tiny particles held in the atmosphere scatter lights of shorter wavelength like blue light…. this light is received by our eye and the sky appears blu… in the absence of atmosphere , scattering does not take place and the sky appears dark….
25. Can visible light be scattered by atoms/molecules in earth’s atmosphere?
Ans. Yes, as size of molecules/atoms i much less then wavelength of light
26. Why does the s y appear ac moue to an astronaut?
Ans. The upper atmosphere does not have particle or dust etc. as a result there is no scattering of light and hence the sky appear dark instead of blue to an astronaut.
27. What is the basic cause of atmospheric refraction?
Ans. The basic cause of refraction is variation in optical density of different layers of earth’s atmosphere. The sun passes through earth’s atmosphere.
28. What is range of vision?
Ans. Range of vision of a normal human eye is between it’s near point and far point is, from 25 cm to infinity.