Q. What is the ratio of luminous intensity of two sources, which produce shadows of equal intensities at distance 25 cm and 50 cm from the photometer screen?
A) 1:4
B) 4:1
C) 1:2
D) 2:1
Explanation
(a) $\frac{I_{1}}{I_{2}} = \frac{r_{1}^{2}}{r_{2}^{2}} = \left( \frac{25}{50} \right)^{2} = \frac{1}{4}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.