Question

A doctor advise a patient to are spectating with a convex len of focal length 40 cm in constant with ·a concave lens of focal length 25 cm. What is the power of the combination?

विकल्प

• – 6.5 D

• – 1.5 D

• 6.5 D

• 1.5 D

Answer 1

– 1.5 D

Explanation:

`1/F = 1/F_1 + 1/F_2`

= `1/40 - 1/25`

= `(5 - 8)/200`

= `(-3)/200`

P = `100/F`

= `(100(-3))/200`

= – 1.5 D