Question

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. $\lambda$

Answer 1

Answer: (C)

$2\,\lambda$

Answer 2

$\beta=\frac{\beta}{\lambda}(\mu-1) t$ $\Rightarrow t=\frac{\lambda}{(\mu-1)}=\frac{\lambda}{(1.5-1)}$ $=2 \lambda$