A hospital uses an ultrasonic scanner to locate tumours in a tissue. What is the wavelength of sound in the tissue in which the speed of sound is 1.7 `kms^-1`? The operating frequency of the scanner is 4.2 MHz.

Calculate the speed of sound in a gas in which two waves of wavelengths 1 . 00 m and 1 . 0 1 m produce 4 beats per second .

A car is moving with a speed of 72 "km-hour"^(-1) towards a roadside source that emits sound at a frequency of 850 Hz. The car driver listens to the sound while approaching the source and again while moving away from the source after crossing it. If the velocity of sound is 340 ms^(-1) , the difference of the two frequencies, the driver hears is