Question

a convex lens of focal length 25 cm and a concave lens
of focal length 10cm are place in close contact with each other. calculate the power of the​

Answer 1

Given:

Focal Length of convex lens, f1=25 cm=0.25 m (since 1 m=100 cm)

Focal Length of convex lens, f2=−10 cm=−0.1 m (since 1 m=100 cm)

Power of convex lens P1=f11=0.25 m1=4 D

∴P1=4 D.

Power of convex lens P2=f21=−0.1 m1=−10 D

∴P2=−10D.

Power of combination =P1+P2=(4−10) D=−6 D.

Thus, power of combination is −6 Dioptre.