Concepts of Physics

IIT JEE Physics (1978-2018: 41 Years) Topic-wise Complete Solutions

Variation of Light Intensity with Distance!


This was demonstrated by Ms Smita Fangaria at Kolkata SRP. Take two bulbs, of different power, say 60 watt and 100 watt. Take sheet of paper. Apply some oil/butter at a spot. This spot becomes translucent. Put two bulbs at some distance, say 1 metre. Move the paper between two sources till intensity on opaque and translucent part of the paper looks same. Measure the distance. See whether \(I\propto\frac{1}{r^2}\).