Question

In young’s double slit experiment light waves of wavelength $5.4 \times 10^{2}$nm and 68.5×10¹nm are used in turn, keeping the same geometry of the set up. The ratio of the fringe width in two cases is:

• A. 1.3
• B. 4.3
• C. 7.9
• D. 9.5

Answer 1

Answer: (C)

7.9

Answer 2

Fringe width $\beta = \frac{D\lambda}{d}$

$\therefore\frac{\beta_{1}}{\beta_{2}} = \frac{\lambda_{1}}{\lambda_{2}} = \frac{5.4 \times 10^{2}}{68.5 \times 10^{1}} = 7.9$