Question

In a certain double slit experimental arrangement interference fringes of width 1.0 mm each are observed when light of wavelength 5000 Å is used. Keeping the set up unaltered, if the source is replaced by another source of wavelength 6000 Å, the fringe width will be.

• A. 0.5 mm
• B. 1.0 mm
• C. 1.2 mm
• D. 1.5 mm

Answer 1

Answer: (C)

1.2 mm

Answer 2

$\frac{\beta_{1}}{\beta_{2}} = \frac{\lambda_{1}}{\lambda_{2}}$or $\frac{1.0}{\beta_{2}} = \frac{5000}{6000}$or $\beta_{2} = \frac{6000}{5000} = 1.2\mspace{6mu} mm$.