Q. In the Young’s double slit experiment, the interference pattern is found to have an intensity ratio between bright and dark fringes as 9. This implies that
A) The intensities at the screen due to two slits are 5 units and 4 units respectively
B) The intensities at the screen due to two slits are 4 units and 1 units respectively
C) The amplitude ratio is 3
D) The amplitude ratio is 2
Explanation
(b) $\frac{I_{\max}}{I_{\min}} = \frac{(a + b)^{2}}{(a - b)^{2}} = 9\ or\ \frac{a + b}{a - b} = 3$
Or $3a - 3b = a + b\ or\ 2a = 4b$;
$\frac{I_{1}}{I_{2}} = \frac{a^{2}}{b^{2}} = \frac{4b^{2}}{b^{2}} = 4:1$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.