Question

A lens of power + 2 diopter 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

Explanation:

P = P1 +P2

  = 2 -1   = 1D = 1m

combination will behave like DIVERGENT

P = 1/f  

f = 100 cm