If a convex lens of focal length 80 cm and a concave lens of focal length 50 cm are combined together, what will be their resulting power?
Answer & explanation
Correct answer: option 4
ResultantPower after combining the two lenses
$ P = P_1 + P_2$
$P_1 = \frac{100}{80} = 1.25D, P_2 = \frac{100}{ -50} = -2 D$
$\Rightarrow P = P_1 + P_2 = 1.25 -2 = -0.75D$