Given below are some examples of wave motion. State in each case, if the wave motion is transverse, longitudinal or a combination both.
(i) Motion of a kink in a long coil spring produced by displacing one end of the string sideways.
(ii) Waves produced in a cylinder containing a liquid by moving its piston back and forth.
(iii) Waves produced by a motor boat sailing in water.
(iv) Light waves travelling from sun to earth.
(v) Ultrasonic waves in air produced by a vibrating quartz crystal.
(i) When the spring is pulled sideways, the kink moves at 90° to the length of the spring. Waves are transverse.
(ii) Waves in this case are longitudinal, because
molecules of the liquid will move along the direction of motion of the piston.
(iii) The water surface is cut laterally and pushed
backwards by the propeller of motor boat. Therefore, the waves are a mixture of longitudinal and transverse waves.
(iv) Light waves (from sun to earth) are electromagnetic
waves which are transverse in nature.
(v) Ultrasonic waves in air are basically sound waves
of frequency greater than the audible frequencies. They are, therefore, longitudinal waves.