Question

A source emitting light of wavelengths 480 nm and 600 nm is used in a double slit interference experiment. The separation between the slit is 0.25mm and the interference is observed ona screen placed at 150 cm from the slits. Find th linear separation between the first maximum (next ot the central maximum) corresponding to he two wavelengths.

Answer 1

We know that, the first maximum (next to central amximum) occurs at y $=\frac{\lambda D}{d}$
Given that, ${\lambda }_1=480nm,{\lambda }_2=600nm,$
D = 150 cm = 1.5m
And d = 0.25 mm
$=0.25\times {10}^{-3}m$
So, $y_1=\frac{D{\lambda }_1}{d}$
$=\frac{\left(1.5\right)\times 480\times {10}^{-9}}{0.25\times {10}^{-3}}=2.88mm{y}_2=\frac{\left(1.5\right)\times 600\times {10}^{-9}}{0.25\times {10}^{-3}}=3.6mm$