First slide

The optical instruments

Question

A person can see clearly only upto a distance of 25 cm. He wants to read a book placed at a distance of 50 cm. What kind of lens does he require for his spectacles and what must be its power

Moderate

A

Concave, – 1.0 D
B

Convex, + 1.5 D
C

Concave, – 2.0 D
D

Convex, + 2.0 D

Solution

For correcting myopia, concave lens is used and for lens.
u = wants to see = -50cm
v = can see = -25 cm
$From \frac{1}{f} = \frac{1}{v} - \frac{1}{u} \Rightarrow \frac{1}{f} = \frac{1}{- 25} - \frac{1}{(- 50)} \Rightarrow f = - 50 cm So power P = \frac{100}{f} = \frac{100}{- 50} = - 2 D$

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