A He-Ne Laser and Diffraction Grating

Calculation of Third Order Maximum Angle

The angle of the third order maximum can be calculated using the formula:

θ = sin^-1(mλ / d)

Where:
θ = angle of diffraction
m = order of maximum (in this case, m = 3)
λ = wavelength of the light (633 nm or 633 x 10^-9 m)
d = distance between slits in the diffraction grating (5.55 x 10^-6 m)

By substituting the values into the formula, we get:
θ = sin^-1(3 * 633 x 10^-9 / 5.55 x 10^-6)
θ = sin^-1(1899 x 10^-9 / 5.55 x 10^-6)
θ = sin^-1(0.000001899 / 0.00000555)
θ = sin^-1(0.34216216216)
θ ≈ 20.0086 degrees

Therefore, the angle of the third order maximum when the He-Ne laser light passes through the diffraction grating is approximately 20.0086 degrees.