First slide

Ray optics

Question

Sun rays are focussed on a photo-sensitive plate with the help of convex lens. The photo-electric current is found to be i. If the lens is replaced by another similar lens of half the diameter and double the focal-length, the photo-current will now be

Easy

A

i / 2
B

i /4
C

i / 8
D

i / 16

Solution

we know that $i \propto D^{2} / f^{2}$
$\frac{i_{1}}{i_{2}} = {(\frac{D_{1}}{D_{2}})}^{2} \times (\frac{f_{2}}{f_{1}}) = (2)^{2} \times (2)^{2} or i_{2} = i_{1} / 16$

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