An object is placed at a distance of 50 cm from a thin lens along the axis.If a real image forms at a distance of 50 cm from the lens,on the opposite side from the object,what is the focal length of the lens?
A) 25 cm
B) 22 cm
C) 200 cm
D) 90 cm

Question

Quizplus · Accepted Answer

The lens formula is 1/f = 1/v + 1/u. Here, v = 50 cm and u = -50 cm (object distance is negative). Solving gives 1/f = 1/50 - 1/50 = 0, so f = 25 cm.

An Object Is Placed at a Distance of 50 Cm