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Science X A,B,C


Date of submission: 2 Jan., 2015


Multiple choice questions

1.Bending of a ray of light,when it enters obliquely from one medium to other is called

a) reflection b) refraction c) dispersion d) scattering

2. A lens converges a ray of light.The lens is

a) concave b) plane c) convex d) plano- concave

3. The relation ,is called

a) Newtons law b) Snell’s law c)Joule’s law d) Boyle’s law

4. When light enters from a rarer medium(medium 1) to a denser medium(medium 2),then n21 has value

a) <1 b)>1 c) 1 d) none of these

5. For light going from air to water nwa=4/3.Then naw has value

a) 16/9 b) 3/2 c) 1 d) ¾

6. A ray of light passes undeviated through a point on the principal axis of a spherical lens. The point is

a) focus b) centre of curvature c) optical centre d) nowhere

7. A thick lens has less focal length. Its power is

a) less b) more c) zero d) infinite

8. A sharp image of an object is obtained on a screen by using a convex lens.Inorder to determine the focal length of the lens you need to measure the distance between

a) lens and the object b) lens and the screen c) object and the screen d) lens and the screen and also object and the screen

9. The mirror which is used as rear view mirror in automobiles is

a) concave mirror b) convex mirror c) plane mirror d) any of these mirrorW

Answer the following questions

1. Define the SI unit of power of a lens.

2. Write mirror formula.

3. Write lens formula.

4. State the laws of refraction

5. Write the relation between radius of curvature and focal length of a spherical mirror.

6. Complete the ray diagram

7.An object of height 3cm is placed at a distance of 9cm in front of concave mirror of focal length 18cm.Find the position ,nature and size of the image formed.

8. An object of height 3cm is placed at a distance of 20cm in front of convex lens of focal length 12cm.Find the position ,nature and size of the image formed.

9. A convex mirror used for rear view on an automobile has R=3m, if a bus is located 3m from the mirror. Find position nature and size of the image.

10. draw the ray diagram in each case to show the position and nature of the image formed when the object is placed:

(i) at the centre of curvature of a concave mirror

(ii) between pole and focus of a concave mirror

(iii) in front of a convex mirror

(iv) at 2f of a convex lens

(v) infront of a concave lens

11. A concave lens has focal length 15cm, at what distance should the object from the lens be placed so that it forms an image at 10cm from the lens.


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