Two lens of power -15 D and +5 D are placed in contact co-axially. The focal length of equivalent lens is:

Two lens of power -15 D and +5 D are placed in contact co-axially. The focal length of equivalent lens is:

A

-10 cm

B

-20 cm

C

+10 cm

D

None

Answer:

The correct option is A. -10 cm

Note