Question

Light from a helium-neon laser (λ=633nm) passes through a circular aperture and is observed on a screen 5.80 mm behind the aperture. The width of the central maximum is 1.70 cm.What is the diameter (in mm) of the hole?

Answer 1

Explanation:

Whenever the light passes through hole or slit then it tends to bend that is actually a diffraction. It will then made the interference pattern of light and dark bands that due to constructive and destructive interference.

So by using the equation of diffraction,

dsinA = nL

SinA is a geometric component it can be written as,

$d\frac{y}{x} = nL$

∵ x is the distance from screen.

∵ y is the half of the width of central maximum.

now by putting the values in mm,

$d\frac{17}{5.80} = 0.000633$

d = 2.15×$10^{-4}$ mm