Two sources P and Q produce notes of frequency 660 Hz. each. A listener moves from P to Q with a speed of 1 ms^$$-$$1. If the speed of sound is 330 m/s, then the number of beats heard by the listener per second will be

A source of unknown frequency gives 4 beats/s when sounded with a source of known frquency 250 Hz. The second harmonic of the source of unknown frequency gives five beats per second, when sounded with a source of frequency 513 Hz. The unknown frequency is

If we study the vibration of a pipe open at both ends. then the following statement is not true.

A wave travelling in the + ve x-direction having displacement along y-direction as 1 m, wavelength 2$$\pi $$ m and frequency of $${1 \over \pi }$$ Hz is represented by