(a)[3]
Show that angle $\theta$ comes out as $49^{\circ}$.
(b)[2]
Determine another wavelength of visible light that would also give a diffraction maximum at an angle of $49^{\circ}$.
Physics 9702 · AS & A Level · The diffraction grating
The diffraction grating — practice question
A beam of red light with wavelength $640\,\text{nm}$ is directed normally onto a diffraction grating whose line spacing is $1.7 \times 10^{-6}\,\text{m}$, as illustrated in Fig. 5.1. The light’s second-order diffraction maximum is observed at an angle $\theta$ to the incident-light direction.