Q. In Young’s double slit experiment, 12 fringes are obtained to be formed in a certain segment of the screen when light of wavelength 600 mm is used. If the wavelength of light is changed to 400 mm, number of fringes observed in the same segment of the screen is given by
A) 12
B) 18
C) 24
D) 30
Explanation
(b) Here, $n_{1} = 12,\ \lambda_{1} = 600\ nm$
$n_{2} = ?,\ \lambda_{2} = 400\ nm$
As $n_{1}\lambda_{1} = n_{2}\lambda_{2}$
$\therefore\ \ \ n_{2} = \frac{n_{1}\lambda_{1}}{\lambda_{2}} = \frac{12 \times 600}{400} = 18$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.