An object of heights 5cm is placed at 20cm from a concave mirror of focal length 10cm. The image height is?

A. 20cm
B. 15cm
C. 10cm
D. 5cm

Correct Answer:

Option D – 5cm

Explanation

(1)/V + (1)/U = (1)/f
(1)/V + (1)/20 = (1)/10
(1)/V = (1)/10 – (1)/20 = (2 -1)/20 = (1)/20
∴ V = 20 cm
mag = (image height)/object height = (v)/u
(X)/5 = (20)/50
X = 5 cm