Question

The radius of curvature of a concave mirror is 20
cm. Where should an object be kept in front of it so
that its real image will formed at 30 cm from
mirror ?​

Answer 1

Answer:

Using Real Is Positive convention — everything here is positive.

f = R/2 = 10 and u = 30

1/v + 1/u = 1/f

1/v = 1/f - 1/u = 1/10 - 1/30 = 3/30 - 1/30 = 2/30 = 1/15

So the image is real, 15cm from the mirror, (midway between object and mirror)

Magnification (v/u) is + 1/2 meaning half size and inverted.