A He-Ne laser (632.8 nm) is used to calibrate a grating. If the first-order maximum occurs at 20.5°, what is the grating constant (the distance between the slits)?
A)0.905 μm
B)1.81 μm
C)2.20 μm
D)3.62 μm
E)4.52 μm

Question

Quizplus · Accepted Answer

The grating equation is d*sin(θ) = m*λ, where d is the grating constant, θ is the angle, m is the order, and λ is the wavelength. For the first-order maximum (m=1), d = λ/sin(θ) = 632.8 nm / sin(20.5°) = 1.81 μm.

A He-Ne Laser (632