Question

A concave mirror which has radius of curvature 30cm produces an image 3× the size of the object. Calculate the mangefication and the object

Answer 1

Given : A concave mirror of radius of curvature 30cm produces a real image three times the size of the object.

To find : The distance between object and image.

solution : radius of curvature of concave mirror, R = 30cm

so, focal length of concave mirror, f = -R/2 = -15 cm

as a real image three times the size of the object.

magnification, m = - 3 [ negative sign indicates image is real]

⇒-v/u = -3

⇒v = 3u(1)

using formula, 1/v + 1/u = 1/f

⇒1/3u + 1/u = 1/-15

⇒4/3u = 1/-15

⇒u = - 20 cm

v = 3u = 3 × -20 = -60cm

Therefore the distance between the object and the image (60cm - 20cm) = 40c