JEE Main & Advanced
Physics
Ray Optics
Question Bank
Critical Thinking
question_answer
The distance between a convex lens and a plane mirror is 10 cm. The parallel rays incident on the convex lens after reflection from the mirror form image at the optical centre of the lens. Focal length of lens will be
A) 10 cm
B) 20 cm
C) 30 cm
D) Cannot be determined
Correct Answer:
B
Solution :
From the figure, Using property of plane mirror Image distance = Object distance f ? 10 = 10 \[\Rightarrow f=20\text{ }cm\]