Question

Two convex lenses of focal length 30 cm and 10 cm each are kept in contact with each other. Find the power of their combination.

Answer 1

Given: f₁ = 30 cm = 0.30 m, f₂ = 10 cm = 0.10 m

To find: Power of combination (P)

Formula: P = `1/"f" = 1/"f"_1 + 1/"f"_2`

Calculation: From formula,

P = `1/"f" = 1/0.30 + 1/0.10 = 1/0.30 + 3/0.30`

`= 4/0.30` = 13.33 D

Power of combination is 13.33 D.