Question

A convex lens and a concave lens, each having same focal length of 25 cm, are put in contact to form a combination of lenses. What is the power in diopters of the combination is

Answer 1

Focal length of convex lens f₁ = 25 cm

Focal length of concave lens f₂ = -25 cm

Power of combination in diopters,

P = P₁ + P₂ = \(\frac{100}{f_1}+\frac{100}{f_2}\) = \(\frac{100}{25}-\frac{100}{25}\) = 0