Question

A plano-convex lens has focal length of 20 cm. If its plane surface is silvered, then new focal length will be –

• A. 10 cm
• B. 15 cm
• C. – 10 cm
• D. – 15 cm

Answer 1

Answer: (C)

– 10 cm

Answer 2

=

Ž =$\frac { - 2 } { + 20 } + \frac { 2 } { \infty }$

\ F = –10 cm