A monochromatic beam of light is directed perpendicularly onto a diffraction grating…
PHYSICS · Multi-part · AP · Physics 2: Algebra-based · Waves Sound and Physical Optics · Waves Sound and Physical Optics
Problem
A monochromatic beam of light is directed perpendicularly onto a diffraction grating that has a very large number of equally spaced slits. An observer notices that, instead of a continuous ring of illumination, a finite set of discrete bright spots appears on a distant screen to either side of the central maximum.
Respond to the prompts below, using clear physical reasoning that references wave interference principles but without performing any detailed numerical calculations.
(a) Explain qualitatively why the grating produces bright spots only at certain discrete angles rather than at every possible angle.
(b) Explain why, for a fixed wavelength of light and a fixed grating, there is an upper limit to the order number of bright spots that can appear. In your explanation, discuss how both the wavelength of the light and the spacing between adjacent slits influence this upper limit.