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.