Given below are some examples of wave motion. State in each case if the wave motion is transverse, longitudinal or a combination of both:
(a) Motion of a kink in a longitudinal spring produced by displacing one end of the spring sideways.
(b) Waves produced in a cylinder containing a liquid by moving its piston back and forth.
(c ) Waves produced by a motorboat sailing in water.
(d) Ultrasonic waves in air produced by a vibrating quartz crystal.

Explanation

(a) When a long spring is given little push or pull, perpendicular to its length and then released, waves progagation on it are transverse.
If a long spring is given little push or pull, parallel to its length and then released, waves propagating in it are longitudinal.
(b) Here given substance is a fluid which cna sustain compressive stress nad can not sustain shearing stress. Hence longitudinal waves can propagate inside it but transverse waves can not propagate in it.
(c ) (i) Free surface of water can sustain shearing stress due to its surface tension peoperty and so transverse waves can propagate on its free surface.
(ii) Part of water medium, below the free surface can sustain compressive stress and so longitudinal waves can propagate in it.
(d) Air is a fluid which can sustain compressive stress but can not sustain shearting stress. Hence longitudinal waves can propagate in air but transverse waves can not.