Question

On introducing a thin mica sheet of thickness $2\times 10^{- 6} \, m$ and refractive index $1.5$ in the path of one of the waves, central bright maxima shifts by $n$ fringes. The wavelength of the wave used is $5000 \, \overset{^\circ }{A}$ , then $n$ is

• A. $1$
• B. $2$
• C. $5$
• D. $10$

Answer 1

Answer: (B)

The shift in no. of fringes is given by
$n\lambda =\left(\mu - 1\right)t$
$n=\frac{\left(\mu - 1\right) t}{\lambda }=\frac{\left(\right. 1.5 - 1 \left.\right) \times 2 \times \left(10\right)^{- 6}}{5000 \times \left(10\right)^{- 10}} \, fringes=2$