(a)[2]
State what the diffraction of a wave means.
(b)[3]
A laser beam of wavelength $500\,\text{nm}$ is directed normally at a diffraction grating. The diffraction pattern produced has diffraction maxima up to and including the fourth-order maximum. Calculate the minimum possible line spacing for the grating.
(c)[2]
The light in (b) is now changed to red light. State and explain whether this is likely to produce a fifth-order diffraction maximum.