Question

If the distance between a point source of light and a screen is made one third, then relation between intensity of light $ \text{(I)} $ and initial intensity $ \text{(}{{\text{I}}_{0}}\text{)} $ will be:

• A. $ \text{I=}\frac{{{\text{I}}_{\text{0}}}}{\text{3}} $
• B. $ \text{I=}\frac{{{\text{I}}_{\text{0}}}}{9} $
• C. $ \text{I=}{{\text{I}}_{\text{0}}} $
• D. $ \text{I=9}{{\text{I}}_{\text{0}}} $

Answer 1

Answer: (D)

Intensity $ I\propto \frac{1}{{{r}^{2}}} $ If distance (r) is made one third, then intensity will become 9 times than the initial intensity.