An ultrasonic grating is a type of diffraction grating[1] produced by the interference of ultrasonic waves in a medium, which alters the physical properties of the medium (and hence the refractive index) in a grid-like pattern.
The human ear cannot recognize ultrasonic waves, but animals such as bats and dogs can.
The less dense antinodes refract light less and are analogous to the transmitting slits of a conventional grating.
The denser nodes refract light more and are analogous to the opaque part of a conventional grating.
is the wavelength of the light passed through the grating that is diffracted by an angle
The Debye–Sears method determines the wavelength of monochromatic light using an acoustic or ultrasonic gratings.
This method utilises the concept of piezoelectricity to obtain a grating.
The phenomenon of diffraction of light using an ultrasonic grating was first observed by Debye and Sears in 1932.
This grating can determine the wavelength of monochromatic light and the speed of waves.
is the wavelength of the ultrasonic waves, then applying the principle of diffraction, we get Where
This method determines the velocity of ultrasonic waves using monochromatic sources like sodium vapour lamps.
The medium is usually a piezoelectric crystal such as quartz, tourmaline, or Rochelle salt.
A mechanical stress is produced along an axis of the crystal using an RF oscillator.