A student uses a diffraction grating to find the wavelength of visible light from a source. The diffraction grating has 300 lines per mm. For each order $n$ of the intensity maxima, the student measures the angle $\theta$. A graph of $n$ against $\sin \theta$ is drawn. The plotted points are fitted with a line of best fit, and this line has gradient $G$. Which expression gives the wavelength, in m, of the visible light in terms of $G$?
- A$3 \times 10^{5} G$
- B$3.3 \times 10^{-6} G$
- C$\frac{3.3 \times 10^{-6}}{G}$
- D$\frac{300}{G}$