SHORT ANSWER QUESTIONS
1. Identify the device used as a spherical mirror or lens in following cases, when the image formed
is virtual and erect in each case.
a. Object is placed between device and its focus, image formed is enlarged and behind it.
b. Object is placed between the focus and device, image formed is enlarged and on the
same side as that of the object.
c. Object is placed between infinity and device, image formed is diminished and between
focus and optical centre on the same side as that of the object.
d. Object is placed between infinity and device, image formed is diminished and between
pole and focus, behind it.
2. Why does a light ray incident on a rectangular glass slab immersed in any medium emerges
parallel to itself? Explain using a diagram.
3. A pencil when dipped in water in a glass tumbler appears to be bent at the interface of air and
water. Will the pencil appear to be bent to the same extent, if instead of water we use liquids
like, kerosene or turpentine. Support your answer with reason.
4. How is the refractive index of a medium related to the speed of light? Obtain an expression for
refractive index of a medium with respect to another in terms of speed of light in these two
media?
5. Refractive index of diamond with respect to glass is 1.6 and absolute refractive index of glass is
1.5. Find out the absolute refractive index of diamond.
6. A convex lens of focal length 20 cm can produce a magnified virtual as well as real image. Is this
a correct statement? If yes, where shall the object be placed in each case for obtaining these
images?
7. Sudha finds out that the sharp image of the window pane of her science laboratory is formed at
a distance of 15 cm from the lens. She now tries to focus the building visible to her outside the
window instead of the window pane without disturbing the lens. In which direction will she
move the screen to obtain a sharp image of the building? What is the approximate focal length
of this lens?
8. How are power and focal length of a lens related? You are provided with two lenses of focal
length 20 cm and 40 cm respectively. Which lens will you use to obtain more convergent light?
9. Under what condition in an arrangement of two plane mirrors, incident ray and reflected ray will
always be parallel to each other, whatever may be angle of incidence. Show the same with the
help of diagram.
10. Draw a ray diagram showing the path of rays of light when it enters with oblique incidence (i)
from air into water; (ii) from water into air.
LONG ANSWER QUESTIONS
11. Draw ray diagrams showing the image formation by a concave mirror when an object is placed
a. between pole and focus of the mirror
b. between focus and centre of curvature of the mirror
c. at centre of curvature of the mirror
d. a little beyond centre of curvature of the mirror
e. at infinity
12. Draw ray diagrams showing the image formation by a convex lens when an object is placed
a. between optical centre and focus of the lens
b. between focus and twice the focal length of the lens
c. at twice the focal length of the lens
d. at infinity
e. at the focus of the lens
13. Write laws of refraction. Explain the same with the help of ray diagram, when a ray of light
passes through a rectangular glass slab.
14. Draw ray diagrams showing the image formation by a concave lens when an object is placed
a. at the focus of the lens
b. between focus and twice the focal length of the lens
c. beyond twice the focal length of the lens
15. Draw ray diagrams showing the image formation by a convex mirror when an object is placed
a. at infinity
b. at finite distance from the mirror
16. The image of a candle flame formed by a lens is obtained on a screen placed on the other side of
the lens. If the image is three times the size of the flame and the distance between lens and
image is 80 cm, at what distance should the candle be placed from the lens? What is the nature
of the image at a distance of 80 cm and the lens?
17. Size of image of an object by a mirror having a focal length of 20 cm is observed to be reduced
to 1/3rd of its size. At what distance the object has been placed from the mirror? What is the
nature of the image and the mirror?
18. Define power of a lens. What is its unit? One student uses a lens of focal length 50 cm and
another of –50 cm. What is the nature of the lens and its power used by each of them?
19. A student focused the image of a candle flame on a white screen using a convex lens. He noted
down the position of the candle screen and the lens as under
Position of candle = 12.0 cm
Position of convex lens = 50.0 cm
Position of the screen = 88.0 cm
a. What is the focal length of the convex lens?
b. Where will the image be formed if he shifts the candle towards the lens at a position of 31.0 cm?
c. What will be the nature of the image formed if he further shifts the candle towards the
lens?
d. Draw a ray diagram to show the formation of the image in case (c) as said above.
20.
a. State the relationship between object distance, image distance and focal length of a spherical mirror.
b. Draw a ray diagram to show the image formation by a concave mirror when an object is placed between pole and focus of the mirror.
c. A concave mirror of focal length 15 cm forms an image of an object kept at a distance of 10cm from the mirror. Find the position, nature and size of the image formed by it.
1. Identify the device used as a spherical mirror or lens in following cases, when the image formed
is virtual and erect in each case.
a. Object is placed between device and its focus, image formed is enlarged and behind it.
b. Object is placed between the focus and device, image formed is enlarged and on the
same side as that of the object.
c. Object is placed between infinity and device, image formed is diminished and between
focus and optical centre on the same side as that of the object.
d. Object is placed between infinity and device, image formed is diminished and between
pole and focus, behind it.
2. Why does a light ray incident on a rectangular glass slab immersed in any medium emerges
parallel to itself? Explain using a diagram.
3. A pencil when dipped in water in a glass tumbler appears to be bent at the interface of air and
water. Will the pencil appear to be bent to the same extent, if instead of water we use liquids
like, kerosene or turpentine. Support your answer with reason.
4. How is the refractive index of a medium related to the speed of light? Obtain an expression for
refractive index of a medium with respect to another in terms of speed of light in these two
media?
5. Refractive index of diamond with respect to glass is 1.6 and absolute refractive index of glass is
1.5. Find out the absolute refractive index of diamond.
6. A convex lens of focal length 20 cm can produce a magnified virtual as well as real image. Is this
a correct statement? If yes, where shall the object be placed in each case for obtaining these
images?
7. Sudha finds out that the sharp image of the window pane of her science laboratory is formed at
a distance of 15 cm from the lens. She now tries to focus the building visible to her outside the
window instead of the window pane without disturbing the lens. In which direction will she
move the screen to obtain a sharp image of the building? What is the approximate focal length
of this lens?
8. How are power and focal length of a lens related? You are provided with two lenses of focal
length 20 cm and 40 cm respectively. Which lens will you use to obtain more convergent light?
9. Under what condition in an arrangement of two plane mirrors, incident ray and reflected ray will
always be parallel to each other, whatever may be angle of incidence. Show the same with the
help of diagram.
10. Draw a ray diagram showing the path of rays of light when it enters with oblique incidence (i)
from air into water; (ii) from water into air.
LONG ANSWER QUESTIONS
11. Draw ray diagrams showing the image formation by a concave mirror when an object is placed
a. between pole and focus of the mirror
b. between focus and centre of curvature of the mirror
c. at centre of curvature of the mirror
d. a little beyond centre of curvature of the mirror
e. at infinity
12. Draw ray diagrams showing the image formation by a convex lens when an object is placed
a. between optical centre and focus of the lens
b. between focus and twice the focal length of the lens
c. at twice the focal length of the lens
d. at infinity
e. at the focus of the lens
13. Write laws of refraction. Explain the same with the help of ray diagram, when a ray of light
passes through a rectangular glass slab.
14. Draw ray diagrams showing the image formation by a concave lens when an object is placed
a. at the focus of the lens
b. between focus and twice the focal length of the lens
c. beyond twice the focal length of the lens
15. Draw ray diagrams showing the image formation by a convex mirror when an object is placed
a. at infinity
b. at finite distance from the mirror
16. The image of a candle flame formed by a lens is obtained on a screen placed on the other side of
the lens. If the image is three times the size of the flame and the distance between lens and
image is 80 cm, at what distance should the candle be placed from the lens? What is the nature
of the image at a distance of 80 cm and the lens?
17. Size of image of an object by a mirror having a focal length of 20 cm is observed to be reduced
to 1/3rd of its size. At what distance the object has been placed from the mirror? What is the
nature of the image and the mirror?
18. Define power of a lens. What is its unit? One student uses a lens of focal length 50 cm and
another of –50 cm. What is the nature of the lens and its power used by each of them?
19. A student focused the image of a candle flame on a white screen using a convex lens. He noted
down the position of the candle screen and the lens as under
Position of candle = 12.0 cm
Position of convex lens = 50.0 cm
Position of the screen = 88.0 cm
a. What is the focal length of the convex lens?
b. Where will the image be formed if he shifts the candle towards the lens at a position of 31.0 cm?
c. What will be the nature of the image formed if he further shifts the candle towards the
lens?
d. Draw a ray diagram to show the formation of the image in case (c) as said above.
20.
a. State the relationship between object distance, image distance and focal length of a spherical mirror.
b. Draw a ray diagram to show the image formation by a concave mirror when an object is placed between pole and focus of the mirror.
c. A concave mirror of focal length 15 cm forms an image of an object kept at a distance of 10cm from the mirror. Find the position, nature and size of the image formed by it.
