Question

Two thin lenses are in contact and the focal length of the combination is 80 cm. If the focal length of one lens is 20 cm, then the power of the other lens will be:

Options

• 1.66 D

• 4.00 D

• −100 D

• −3.75 D

Answer 1

−3.75 D

Explanation:

P₂ = P − P₁

= `100/80 - 100/20`

= −3.75 D