Diffraction grating is an array of a large number of parallel, evenly spaced slits of the same width.
- When light is shone through a diffraction grating, bright and sharp fringes can be observed at several angular position with the aid of a spectrometer
$d \, sin \, \theta = m \lambda$, where d is slit separation, m is the order of the fringe
Maximum possible order: $m < \frac{d}{\lambda}$, as $\theta$ must be less than $90^{o}$.
