Explain about the principle of acousting grating.

Acousting Grating Principle:

While ultrasonic waves are passed by a liquid, the density of the liquid varies layer by layer because of the variation in pressure and therefore the liquid will act as a diffraction grating that is termed as acoustic grating. Under that condition, while a monochromatic source of light is passed by the acoustical grating, then the light gets diffracted. After that, by using the condition for diffraction, the velocity of ultrasonic waves can be found out.