Q. In a double slit experiment, when light of wavelength 400 nm was used, the angular width of the first minima formed on a screen placed 1m away, was found to be 0.2°. What will be the angular width of the first minima, if the entire experimental apparatus is immersed in water ($\mu_{water} = 4/3$)
A) 0.266°
B) 0.15°
C) 0.05°
D) 0.1°
Explanation
[Solution] Angular width $\propto \lambda$; in water $\lambda' = \lambda/\mu$, so width = 0.2 × 3/4 = 0.15°. Answer (2).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.