Question

In order to obtain a magnification of, –0.75 with a convex lens of focal length 8 cm, the object should be placed
(a) at less than 8 cm
(b) between 8 cm and 16 cm
(c) beyond 16 cm
(d) at 16 cma

Answer 1

Answer:[d]

beyond

16 cm

Explanation: here the magnification is negative.

so the image is real and inverted.

also as m=v/u for a given lens

this implies that  v=-3u/4.

hence the image is smaller than the object.

so it is placed beyond c i.e. beyond 16 cm.

P.S.==> this could be proved by actual calculations but i am very tired.;]

Answer 2

In order to obtain a magnification of, –0.75 with a convex lens of focal length 8 cm, the object should be placed beyond 16 cm.

Explanation:

• For an object placed beyond 16 cm of a convex lens, the real image occurs.
• The rays diverge when there is an occurrence of the virtual image.
• By converging lenses and concave mirrors, real images can be formed, only if there is a placement of object further away from the lens/mirror than the focal point.