Mechanism
When ultrasonic waves are generated in a liquid kept in rectangular vessel, the wave can be reflected from the walls of the vessel.These reflected waves are called echos. The direct and reflected waves get superimposed, which causes a standing wave to be formed. The density of the liquid at the node will be more than the density at an antinode. Under these conditions, if a parallel beam of light is passed through the liquid at right angles to the wave the liquid acts as a diffraction grating. Such a grating is known as an acoustical grating.
Here, the antinode acts as the transmitting slit and the node acts as the opaque part...thus resembling a normal ruled diffraction grating. This is obvious because the antinodes have points of minimum density and hence allow more amount of light to pass through them than those at nodes. Thus, the antinodes act like slits.
Read more about this topic: Ultrasonic Grating
Famous quotes containing the word mechanism:
“A mechanism of some kind stands between us and almost every act of our lives.”
—Sarah Patton Boyle, U.S. civil rights activist and author. The Desegregated Heart, part 3, ch. 2 (1962)
“The two elements the traveler first captures in the big city are extrahuman architecture and furious rhythm. Geometry and anguish. At first glance, the rhythm may be confused with gaiety, but when you look more closely at the mechanism of social life and the painful slavery of both men and machines, you see that it is nothing but a kind of typical, empty anguish that makes even crime and gangs forgivable means of escape.”
—Federico García Lorca (1898–1936)
“I’ve never known a Philadelphian who wasn’t a downright “character;” possibly a defense mechanism resulting from the dullness of their native habitat.”
—Anita Loos (1888–1981)