Question

If each two concave lenses of focal length 30 cm are kept in contact with each other what will be the power of combination?

Answer 1

Given: f₁ = f₂ = – 30 cm = – 0.3 m

To find: Power of combination (P)

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

Calculation: From formula,

P = `1/(- 0.3) + 1/(- 0.3)`

`= (- 10)/3 + (- 10)/3`

`= (- 20)/3` = - 6.7 D

Power of combination is – 6.7 D.