QuestionBank of Light PDF
QuestionBank of Light PDF
QuestionBank of Light PDF
(b) When an object is placed between the focus and the pole of
concave mirror than the image formed will be virtual, erect,
magnified and formed behind the mirror.
15. State two uses of (a) concave mirror (b) convex mirror.
Ans. (a) Uses of concave mirror:
(i) as a shaving mirror.
(ii) as a reflector in the headlights of automobiles.
(b) Uses of convex mirror:
(i) as a rear view mirror.
(ii) as a street light reflector.
16. State two differences between a real image and a virtual image.
Ans. (i) Real image can be obtained on screen whereas virtual image
cannot be obtained on screen.
(ii) Real image is always inverted whereas virtual image is always
erect.
Class-VII Physics 15 Question Bank
17. You are provided with(a) plane mirror (b) concave mirror (c)convex
mirror. How will you distinguish them without touching?
Ans. We can distinguish different types of mirror on the basis of image
formation of an object.
(a) A plane mirror always forms an erect and equal-sized image of
an object.
(b) A concave mirror forms an inverted and enlarged image of an
object.
(c) A convex mirror always forms an erect and small-sized image
of an object.
18. What is a concave mirror?
Ans. A spherical mirror, which is polished from outer curved side. Such
that its reflecting surface is towards the hollow side is called concave
mirror.
19. Where should you keep the object to get a real, enlarged image with
a concave mirror?
Ans. When we keep the object between principal focus (F) and centre of
curvature (C) of concave mirror then the image will be real, enlarged
and formed beyond the centre of curvature but not at infinity.
20. What property of concave mirrors is used in making of search light?
Ans. If a point source of light is placed at the focus of a concave mirror,
the rays of light starting from focus, after reflection from the mirror
are rendered parallel to the principal axis. This property of concave
mirror is used in the making of search light.
21. What types of mirror is used as a rear-view mirror in vehicles and why?
Ans. Convex mirror is used as a rear-view mirror in vehicle.
The images formed by convex mirror are erect and smaller in size
and formed behind the mirror. Because of this property, convex
mirrors are used by bus or car drivers to get a wide view of whole
traffic coming from behind.
22. Monica, 145 cm tall stood at a distance of 2 metres away from a
plane mirror.
(a) What is the distance between Monika and her image?
Class-VII Physics 16 Question Bank
(b) What will be the height of Monika’s image?
(c) What will be the distance between Monika and her image if
she walks a distance of 1 m towards the mirror?
(d) How much further she has to walk to be only 1 m from her image.
Ans. (a) We know that in a plane mirror, the image formed on the same
distance as the distance between object and mirror. So, the
distance between Monika and her image
= 2 + 2 = 4 metres.
(b) The height of Monika will be same i.e., 145 cm.
(c) If Monika walks a distance of 1 metre towards the mirror then
there will be short of two metres in total distance.
i.e., 4 – 2 = 2 metres
(d) She has to walk only ½ metre further (total 1½ m) to be only
1 metre from her image.