Question

Ankit the convex and concave lens and kept in contact what are the resultant focal length and focal power of the system ?

A. Infinity, 0
B. 0,0
C. 0, Infinity
D. Infinity,Infinity​

Answer 1

Given:

Ankit has convex and concave lens of equal focal length and kept in contact

To find:

what are the resultant focal length and power of the system ?

Calculation:

• The net focal length refers to the distance between the the combination of lens and point where parallel rays of light meet the principal axis after refraction.

• The net power of the combination of lens refers to the converging or diverging capability.

$\therefore \: P_{net} = P_{1} + P_{2}$

$\implies \: P_{net} = \dfrac{1}{f_{1}} + \dfrac{1}{f_{2}}$

$\implies \: P_{net} = \dfrac{1}{f} + \dfrac{1}{( - f)}$

$\implies \: P_{net} = \dfrac{1}{f} - \dfrac{1}{f}$

$\boxed{ \implies \: P_{net} = 0}$

$\implies \: \dfrac{1}{f_{net}} = 0$

$\implies \: f_{net}= \dfrac{1}{0}$

$\boxed{\implies \: f_{net}= \infty}$

$\boxed{ \bold{Option \: \: C }}$