In: Physics
Monochromatic light of intensity I0=24.0
W/m2 is shone through two slits a distance d=2.2mm
apart. A screen a distance L=1.0m away from the slits shows the
resulting interference pattern.
If at y=8.3cm from the center of the screen the intensity
I=10.2W/m2, what is the wavelength of the light λ (in
μm)?
The intensity formula can be written as I = Io
cos2[dy/L]
where Io is the maximum intensity on the screen, Io = 4I, where
Iinc is the intensity of the incident light.
Given that d = 2.2 x 10-3 m
y = 8.3 x 10-2 m, L = 1 m
cos2[dy/L]
= I/Io
= 10.2/(4 x 24) = 0.10625
Taking square root on both the sides,
cos[dy/L]
= 0.326
[dy/L]
= cos-1(0.326) =
1.239
[Angles are in radians]
= [ x (2.2 x
10-3) x (8.3 x 10-2)] / [1.239 x 1]
= 463.08 x 10-6 m