Question

In Young's double slit experiment $62$ fringes are visible in the field of view with sodium light $(\lambda =5893\AA )$. If green light $(\lambda =5461\AA )$ is used then the number of visible fringes will be

• A. $62$
• B. $67$
• C. $85$
• D. $58$

Answer 1

The correct option is B $67$

Wavelength of light used is inversely proportional to number of fringes observed.
$\therefore {\lambda }_s{n}_s={\lambda }_g{n}_g$
$n_g=\frac{{\lambda }_s{n}_s}{{\lambda }_g}=\frac{5893\times 62}{5461}$
$=66.9\approx 67$