When considering light moving through a diffraction grating, you should treat the light as what?

Wave

Explanation:

The dual nature of light is manifested through its behavior as a particle and as a wave depending on the experimental set-up.

Here, a diffraction grating is an optical component which splits falling on it, into characteristic wavelengths. The grating equation is given as:

where n = diffraction order 1,2,3...

λ=wavelength of light

d=distance between the grooves (lines) on the grating

θ=dispersion angle

since the wavelength of light (λ, in nanometers) is comparable to the length of the medium with which the light interacts which in this case is the value of 'd'; the light is treated as a wave.

Situations where the wavelength of light is not comparable with the length scale of the interaction medium, light is treated as a particle.