Diffraction grating

special case of multi-slit diffraction The diffraction grating equation is given by:

$$a(\sin {\theta }_m-\sin {\theta }_i)=m\lambda$$

where $a$ is the spacing between the gratings, ${\theta }_i$ is the incident angle, and ${\theta }_m$ is the diffracted angle. We follow a sign convention: ${\theta }_{m,i}>0$ if the ray points upwards, and ${\theta }_{m,i}<0$ if the ray points downwards.

separation of widths is the width length?

Applications

Diffraction gratings can be used as spectrometers.