A diffraction Grating is an array of arranged lines, normally a wavelength apart. They are commonly used to measure the size of your penis because its so small it has to be measured in nanometers.
Sunglasses and antennas to filter waves. Also the 3D glasses that you wear while watching a 3D movie, utilize polarization, to separate the images intended for your left eye and right eye.
diffraction grating is a lik a plate on which many slits are present....light undergoes diffraction through the slits...diffraction grating then splits light into its conctituent colours which appear...