Level – 2

1. Explain why a ray of light passing through the centre of curvature of a concave mirror gets
reflected along the same path after reflection?
2. To construct a ray diagram we use two rays of light which are so chosen that it is easy to
determine their directions after reflection from the mirror. Choose these two rays and state the
path of these two rays after reflection from a concave mirror. Use these two rays to find the
nature and positions of the image of an object placed at a distance of 15 cm from a concave
mirror of focal length 10 cm.
3. A concave mirror is immersed in water. What change, if any, do you expect in the focal length of
the mirror?
4. If light is entering from air (n=1) to water (1.33), which is rarer medium?
5. Refractive indices of a few objects are given below; arrange them in the ascending order of the
speed of light in them.
2.4, 1.5, 1.24, 1.75, 2.1, 1.2, 3.6, 5
6. If the velocity of light in certain medium is 2.4*108 m/s, what is the refractive index of the
medium?
7. Absolute refractive index of glass is 3/2. Absolute refractive index of water is 4/3. What is the
refractive index of water with respect to glass?
8. Refractive index of glass with respect to water is 1.12. If the refractive index of water is 1.33,
what is the absolute refractive index of the glass?
9. When light enters from medium 1 to medium 2, the angle of refraction is greater than that of
angle of incidence. Which medium is denser? Why?
10. The absolute refractive index of 2 media ‘A’ and ‘B’ are 2.0 and 1.5 respectively. If the speed of
light in medium ‘B’ is 2 × 10 8 m/s, calculate the speed of light in: (i) vacuum (ii) medium ‘A’.
11. An object 5cm height is placed at a distance of 12cm. in front of a concave mirror it forms a real
image 4times large than the image calculate the distance of the image from the mirror
12. An object is placed at 20 cm in front of a convex mirror of focal length 10 cm. Find the image
distance and magnification.
13. Write some applications of concave and convex lens
14. Object is placed at a distance 10 cm from a convex mirror of focal length 15 cm. what will be the
nature the image?
15. Define Refractive Index.
16. A coin in a glass beaker appears to rise as the beaker is slowly filled with water. Why?
17. An object under water appears to be at lesser depth than in reality. Explain why?
18. A ray of light travelling in air enters obliquely into water. Does the light ray bend towards the
normal or away from the normal? Why?
19. State two conditions under which a ray of light suffering refraction from medium 1 to medium 2
does not undergo any change in direction.
20. Why the power of a lens is is measured as reciprocal of focal length? Give reason.
21. A convergent lens of power 8D is combined with a divergent lens of power -10 D. Calculate focal
length of the combination.
22. Under what condition in an arrangement of two plane mirrors, incident ray and reflected ray will
always be parallel to each other, whatever be the angle of incidence? Show the same with the help
of diagram.
23. If an object of height 4 cm is placed at distance of 12 cm from a concave mirror having focal
length 24 cm, find the position, nature and the height of the image.
24. An object of height 6 cm is placed at a distance of 10 cm from a convex mirror with radius of
curvature 30 cm. Find the position, nature and the height of its image.
25. At what distance the object should be placed so that the image will be formed at a distance 10 cm
from a concave lens? Focal length of the lens is 20 cm.
26. A student has to trace the path of a ray of light through a glass prism. List four precautions he
should observe for better results.
27. Draw a labeled ray diagram to show the path of the reflected ray corresponding to an incident ray
of light parallel to the principal axis of a convex mirror. Mark the angle of incidence and the
angle of reflection on it.
28. A concave mirror has a focal length of 20 cm. At what distance from the mirror should a 4 cm tall
object be placed so that it forms an image at a distance of 30 cm from the mirror? Also calculate
the size of the image formed.
29. 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 the size of the
image formed. Draw a labeled ray diagram showing object distance, image distance and focal
length in the above case.
30. List four characteristics of the image formed by a concave mirror of focal length 40 cm when the
object is placed in front of it at a distance of 20 cm from its pole.
31. 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.
32. What is meant by the 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.
33. An object of height 4 cm is placed at a distance of 30 cm from the optical centre ’O’ of a convex
lens of focal length 20 cm. Draw a ray diagram to find the position and the size of the image
formed. Mark the optical centre ‘O’ and the principal focus ‘F’ on the diagram. Also find the
approximate ratio of size of the image to the size of the object.
34. Between which two points of a concave mirror should an object be placed to obtain a
magnification of – 3?
35. Distinguish between a real and a virtual image of an object. What type of image is formed
(i) by a plane mirror (ii) on a cinema screen?
36. What is the principle of reversibility of light? Show that the incident ray of light is parallel to the
emergent ray of light when light falls obliquely on a side of a rectangular glass slab.
37. A lens of focal length 20 cm is used to produce a ten times magnified image of a film slide on a
screen. How far must the slide be placed from the lens?
38. An object 60 cm from a lens gives a virtual image at a distance of 20 cm in front of the lens.
What is the focal length of the lens? Is the lens converging or diverging? Give reasons for your
answer.
39. A lens A produces a magnification of -0.6 whereas lens B produces a magnification of +0.6.
What is the nature of lens A and B?
40. An object of height 2 cm is placed at a distance of 15 cm in front of a concave lens of power
-10D. Find the size of the image.