Chapter wise Important Qustions |chapter 10|Light Reflection and Refraction|Class 10 |SCIENCE


1.What is meant by power of a lens? Write its SI unit. A student uses a lens of focal length 40 cm and another of -20  cm. Write the nature and power of each lens.

2.State the laws of refraction of light. Explain the term ‘absolute refractive index of a  medium’  and  write  an expression to relate it with the speed of light in vacuum.
3.(a)Define principal focus of a spherical mirror.
(b) For what position of the object does a concave mirror form a real, inverted and diminished image of the object? Draw the ray diagram.

4.An object 4 cm high is placed at a distance of 6 cm in front of a concave mirror of focal length 12 cm. Find the position of the image formed

5.Which lens can be used as a magnifying glass? For which position of object does a convex lens form:
a).a virtual and erect image?
b).a real and inverted image of same size as that of object? Draw labelled ray diagrams to show the formation of the required image in each of the above two cases.

6.(a) Write one use of concave mirror as well as convex mirror.
(b) Draw ray diagrams for the following cases when a ray of light:
(1)passing through centre of curvature of a concave mirror is incident on it.
(2) parallel to principal axis is incident on convex minor.
(3)is incident at the pole of a convex mirror.
(4) passing through focus of a concave mirror  incident on it.
7.(a) Explain the following terms related to spherical lenses:
(i) Optical centre   (ii) Centres of curvature
(iii) Principal axis   (iv) Aperture
(v) Principal focus (vi)Focal length
(b) A converging lens has focal length of 12 cm. Calculate at what distance should the object be placed from the lens so that , it forms an image at 48 cm on the other side of the lens.

8 .A 5 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 20 cm. The distance of the object from the lens is 30 cm.  Find the  position ,  nature  and size of the image formed.

9..The focal length of a concave mirror is 30 cm. Find the position of the object in front of the mirror so that the image is three times the size of the object.

10.A 10 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 30 cm. The distance of the object from the lens is 20 cm. Find the (i) position, (ii) nature and (iii) size of the image formed.

11.a) A concave mirror produces three times enlarged image of an object placed at 10 cm in front of it. Calculate the focal length of the mirror.
(b) Show the formation of the image with the help of a ray diagram when object is placed 6 cm away from the pole of a convex mirror.

12. Define the following terms in relation to concave spherical mirror:
(i)Pole   (ii)Centre of curvature
(iii)Radius of curvature    (iv)Principal axis
(v)Principal focus  (vi)Aperture
(vii) Focal length

13..If the image formed by a convex lens is of the same size as that of the object. What is the position and nature of the image with respect to the lens?
(a) What happens to a ray of fight when it travels from one medium to another having equal refractive indices?
 (b) State the cause of refraction of fight
14.(a) Name the spherical mirror used as:
(i) Shaving mirror,
(ii) Rearview  mirror in vehicles,
(iii) Reflector in search – fights.
(b) Write any three differences between a real and virtual image.

15.Differentiate between reflection and refraction of light.


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