Question

A lens of power +2 diopters is placed in contact with a lens of power ­1 diopter. The combination will behave like

(a)  A convergent lens of focal length 50 cm

(b)  A divergent lens of focal length 100 cm

(c)  A convergent lens of focal length 100 cm

(d)  A convergent lens of focal length 200 cm

Answer 1

Correct option  (c) A convergent lens of focal length 100 cm 

Explanation :

P_er = P₁ + P₂ = +2D ­- 1D = + 1D

f = 1/P_er = 1/1D = 100cm or 1 cm