Q. On introducing a thin film in the path of one of the two interfering beams, the central fringe will shift by one fringe width. If $\mu - 1.5,\ $the thickness of the film is (wavelength of monochromatic light is $\lambda$)
A) $4\lambda$
B) $3\lambda$
C) $2\lambda$
D) $\lambda$
Explanation
(c) $\beta = \frac{\beta}{\lambda}(\mu - 1)t\ $
$\Rightarrow t = \frac{\lambda}{(\mu - 1)} = \frac{\lambda}{(1.5 - 1)} = 2\lambda$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.