An observer moves towards a stationary source of sound with a speed 1/5^th of the speed of sound. The wavelength and frequency of the source emitted are $$\lambda $$ and $$f$$ respectively. The apparent frequency and wavelength recorded by the observer are respectively

A whistle revolves in a circle with angular speed $$\omega $$ = 20 rad/s using a string of length 50 cm. If the frequency of sound from the whistle is 385 Hz, then what is the minimum frequency heard by an observer which is far away from the centre (velocity of sound $$=$$ 340 m/s)

A wave travelling in positive X-direction with a $$=$$ 0.2 ms^$$-$$2, velocity = 360 ms^$$-$$1 and $$\lambda $$ $$=$$ 60 m, then correct expression for the wave is

Two waves having equation x₁ = $$a$$sin($$\omega $$t $$-$$ kx + $$\phi $$₁), x₂ = asin($$\omega $$t $$-$$kx + $$\phi $$₂). If in the resultant wave the frequency and amplitude remain equal to amplitude of superimposing waves, the phase difference between them is