Question

A lens of power +3.5 diopters is placed in contact with a lens of power -2.5 diopter. The combination will behave like:

• A. A convergent lens of focal length 100 cm
• B. A divergent lens of focal length 100 cm
• C. A convergent lens of focal 200 cm
• D. A divergent lens of focal length 200 cm

Answer 1

Answer: (C)

A convergent lens of focal 200 cm

Answer 2

$P = P_ 1 + P_2 = + 2 -1 = 1.$ It is a convergent lens of focal length 100 cm