Lakhmir Singh Physics Class 10 Solutions Page No:207
Question 37: The diagrams show the appearance of a fork when placed in front of and close to two mirrors A and B, turn by turn.
(a) Which mirror is convex?
(b) Which mirror is concave?
Solution : (a) Mirror B is convex since it forms a smaller image of fork.
(b) Mirror A is concave since it forms a larger image of fork.
Question 38: The diagram shows a dish antenna which is used to receive television signals from a satellite. The antenna (signal detector) is fixed in front of the curved dish.
(a) What is the purpose of the dish?
(b) Should it be concave or convex?
(c) Where should the antenna be positioned to receive the strongest possible signals?
(d) Explain what change you would expect in the signals if a larger dish was used.
Solution : (a) The purpose of the dish is to collect a large amount of TV signals from the satellite.
(c) At the focus of the dish.
(d) Stronger signals will be received.
Question 39: A man standing in front of a special mirror finds his image having a very small head, a fat body and legs of normal size. What is the shape of :
(a) top part of the mirror ?
(b) middle part of the mirror ?
(c) bottom part of the mirror ?
Give reasons for your choice.
Solution : (a) Convex – Because a convex mirror forms a diminished image when the object is placed near it.
(b) Concave – Because a concave mirror forms an enlarged image when the object is placed near it.
(c) Plane – Because a plane mirror forms an image of same size as the object.
Question 40: Two big mirrors A and B are fitted side by side on a wall. A man is standing at such a distance from the wall that he can see the erect image of his face in both the mirrors. When the man starts walking towards the mirrors, he finds that the size of his face in mirror A goes on increasing but that in mirror B remains the same
(a) mirror A is concave and mirror B is convex
(b) mirror A is plane and mirror B is concave
(c) mirror A is concave and mirror B is convex
(d) mirror A is convex and mirror B is plane
Solution : (c) Mirror A is concave and mirror B is concave