First slide

Ray optics

Question

Focal length of a convex lens made of crown glass is 20 cm. An achromatic lens is to be made by keeping two lenses, one made of crown glass and the other made of flint glass, in contact with each other. If dispersive power of crown glass is 0.016 and that of flint glass is 0.03, find the focal length of the lens made of flint glass.

Moderate

A

32.75 cm, concave
B

28.5 cm, concave
C

19.5 cm, convex
D

37.5 cm, concave

Solution

For achromatic combination,
$\frac{ω}{f} + \frac{ω'}{f'} = 0 \Rightarrow f' = - f \frac{ω'}{ω} = - 20 x \frac{0.03}{0.016} cm = - 37.5 cm$

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App