# NCERT Solutions for Class 10 Science

Find 100% accurate solutions for NCERT Class X Science. All questions have been explained and solved step-by-step, to help you understand thoroughly. Free Download option available!

# Light Reflection and Refraction

Exercise 1

1.    Which one of the following materials cannot be used to make a lens?

(a) Water                                (b) Glass

(c) Plastic                               (d) Clay

2.    The image formed by a concave mirror is observed to be virtual, erect and larger than the object. Where should be the position of the object?

(a) Between the principal focus and the centre of curvature.

(b) At the centre of curvature

(c) Beyond the centre of curvature

(d) Between the pole of the mirror and its principal focus.

3.     Where should an object be placed in front of convex lens to get a real image of the size of the object?

(a) At the principal focus of the lens.

(b) At twice the focal length

(c) At infinity

(d) Between the optical centre of the lens and its principal focus.

4.     A spherical mirror and thin spherical lens have each of focal length of -15 cm. the mirror and lens are likely to be

(a) Both concave

(b) Both convex

(c) The mirror is concave and the lens is convex

(d) The mirror is convex and lens is concave.

5.     No matter how far you stand from a mirror, your image appears erect. The mirror is likely to be

(a) Plane                                   (b) Concave

(c) Convex                                 (d) Either concave or convex.

6.     Which of the following lens would you prefer to use while reading small letters found in a dictionary?

(a) A convex lens of focal length 50 cm

(b) A concave lens of focal length 50 cm

(c) A convex lens of focal length 5 cm

(d) A concave lens of focal length 5 cm

7.     We wish to obtain an erect image of an object, using a concave mirror of focal length 15 cm. What should be the range of distance of the object from mirror? What is the nature of image? Is the image larger or smaller than the object? Draw a ray diagram to show the image formation in this case.

8.     Name the type of mirror used in the following situations:

(b) Side/rear-view mirror of a vehicle.

(c) Solar furnace.

9.    One-half of a convex lens is covered with a black paper. Will this lens produce a complete image of the object? Verify your answers experimentally. Explain your observations.

10.   An object 5 cm in length is held 25 cm away from a converging lens of focal length 10 cm. Draw the ray diagram and find the position, size and the nature of the image formed.

11.    A convex lens of focal length 15 cm forms an image 10 cm from the lens. How far is the object placed from the lens? Draw the ray diagram.

12.   An object is placed at a distance of 10 cm from a convex mirror of focal length 15 cm. Find the position and nature of image.

13.   The magnification produced by a plane mirror is +1. What does this means?

14.   An object 5.0 cm in length is placed at a distance of 20 cm in front of a convex mirror of radius of curvature 30 cm. Find the position of the image, its nature and size.

15.   An object of size 7.0 cm is placed at 27 cm in front of a concave mirror of focal length 18 cm. At what distance from the mirror should a screen be placed, so that a sharp focused image can be obtained? Find the size and the nature of the image.

16.   Find the focal length of a lens of power -2.0 D. What type of lens is this?

17.   A doctor has prescribed a corrective lens of power +1.5D. Find the focal length of the lens. Is the prescribed lens diverging or converging?

Exercise 2

18.   Define the principle focus of a concave mirror.

19.   The radius of curvature of a spherical mirror is 20 cm. what is its focal length?

20.  Name a mirror that can give an erect and enlarged image of an object.

21.   Why do we prefer a convex mirror as a rear-view mirror in vehicles?

Exercise 3

22.  Find the focal length of a convex mirror whose radius of curvature is 32 cm.

23.  A concave mirror produces three times magnified real image of an object placed at 10 cm in front of it. Where is the image located?

Exercise 4

24.  A ray of light traveling in air enters obliquely into water. Does the light ray bend towards or away from the normal? Why?

25.  Light enters from air to glass having refractive index 1.50. What is the speed of light in glass? The speed of light in vacuum is 3 x 108 m/s.

26.  Find out, from Table (10.3), the medium having highest optical density. Also, find the medium with lowest optical density.

27.  You are given kerosene, turpentine and water. in which of these does the light travel fastest? Use the information given in table 10.3

28.  The refractive index of diamond is 2.42. What is the meaning of this statement?

Exercise 5

29.  Define 1 dioptre of power of lens.

30.  A convex lens forms a real and inverted image of a needle at distance of 50 cm. from it. Where is the needle placed in front of the convex lens if the image is equal to the size of objects? Also, find the power of lens.

31.  Find the power of a concave lens of focal length 2 m.

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