Question

An object of 5.0cm in size is placed at a distance of 20.0cm from a concave mirror of focal length 15.0cm.At what distance from the mirror should a screen be placed to get a sharp images? Also calculate size of the image​

Answer 1

If the focal length is -15 the center of curvature will be 30 since it is a concave mirror the image formed will be positive.

the size will be 1/v +1/u=1/f

so,1/v=1/f-1/u=1/-15 - 1/-20 = -1/15 + 1/25

or 1/v=-2/75 v=-37.5

also magnification m will be m=h'/h =-v/u

height of the image h = -6 cm

the image is real and inverted