Question

White coherent light (400 nm-700 nm) is sent through the slits of a Young's double slit experiment (figure 17-E3). The separation between the slits is 0.5 mm and the screen is 50 cm away from the slits. There is a hole in the screen at a point 1.0 mm away (along the width of the fringes) from the central line. (a) Which. wavelength(s) will be absent in the light coming from the hole ? (b) which wavelength(s) will have a strong intensity ?

Answer 1

Given that, λ= (400 nm to 700 nm), d = 0.5 mm = 0.5x10^–3 m,
D = 50 cm = 0.5 m and on the screen y_n = 1 mm = 1x10^–3 m
a) We know that for zero intensity (dark fringe)

So, the light waves of wavelengths 400 nm and 667 nm will be absent from the out coming light.
b) For strong intensity (bright fringes) at the hole

So, the only wavelength which will have strong intensity is 500 nm.