Question

Q. 8. Two thin lenses having optical powers of -10 D
and + 6 D are placed in contact with each other.
The focal length of the combination is :
(a) + 0.25 cm (b) - 0.25 cm
(c) + 0.25 m (d) - 0.25 m
[ISC 2016]​

Answer 1

Answer:

let, P1= -10D

P2= 6D

TOTAL POWER= -10+6 = -4D

Therefore the focal length will be

f = 1/p(m)

f = 1/-4

f = -4