Study the behaviour of a 15kHz ultrasonic wave as it moves from air into glycerine.
(a) Derive an expression relating the wavelengths λ1 and λ2 of a sound wave in two different media to the corresponding speeds v1 and v2, assuming that frequency remains constant during transmission.
(b) Using the expression, calculate the wavelength of the ultrasonic wave in glycerine if the speed of sound in air is 340m/s and in glycerine is 1900m/s.
(c) Explain briefly how the change in wavelength obtained in part (b) helps ultrasonic waves clean fine cavities in industrial components.