Question

An object is placed at 27 cm in front of a concave mirror of focal length 18 cm. At what distance from the mirror should a screen be placed in order to obtain a sharp image ?​

Answer 1

Answer:

We are given a concave mirror which has a focal length of 18 cm. An object of height 7 cm is placed in front of the concave mirror such that it is 27 cm away from the mirror. The image of the object which was kept 27 cm away from the mirror is formed at 54 cm in front of the mirror.

Answer 2

Answer:

Given that

u = – 27 cm

f = – 18 cm

h0 = 7.0 cm

Find out

We need to find out size and nature of image

Formula

We know the mirror formula that

1/v = 1/f- 1/u

1/v = -1/18 + 1/27 = -1/54

V = – 54 cm

The screen must be placed at a distance of 54 cm from the mirror in front of it.

hi/h0= v/u

hi/h0= v/u

hi/7 = +54/-27 hi= -2 x 7 = -14 cm.

Thus, the image is of 14 cm length and is inverted image