Question

In two separate setups of young's double slit experiment, fringes of equal width are observed when lights of wavelengths in the ratio 2: 1 are used. If ratio of slit separation in two cases is 2 : 1, the ratio of distances between the plane of slits and the screen in the two setups is –

• A. 4 : 1
• B. 1 : 1
• C. 1 : 4
• D. 2 : 1

Answer 1

Answer: (B)

1 : 1

Answer 2

$\frac{D_{1}\lambda_{1}}{d_{1}}$ = $\frac{D_{2}\lambda_{2}}{d_{2}}$

$\frac{D_{1}}{D_{2}}$= $\frac{\lambda_{2}}{\lambda_{1}}$. $\frac{d_{1}}{d_{2}}$= $\frac{1}{2}$ × $\frac{2}{1}$= 1