Diffraction grating : Diffraction grating is an extremely useful device. In one of its form it consists of a very large number of narrow slits side by side. The slits are separated by opaque spaces.
Diffraction gratings are of two types; transmission grating and reflection grating.
- Transmission grating: When a wavefront is
incident on a grating surface light is transmitted through the slits and
obstructed by the opaque portion. Such a grating is called a transmission
- Reflection grating: When the lines of grating surface are drawn on a slivered surface then light is reflected from the position of the mirror in between any two lines. Such surfaces act as reflection gratings.