Which one of the following statements is true ?

A point source emits sound equally in all directions in a non-absorbing medium. Two points P and Q are at distances of 2 m and 3 m respectively from the source. The ratio of the intensities of the waves at P and Q is

The phase difference between two waves. represented by
y₁ = 10^$$-$$6 sin[100t + (x/50) + 0.5] m
y₂ = 10^$$-$$6 cos[100t + (x/50)] m,
where x is expressed in metres and t is exressed in secondss, is approximately.

A car is moving towards a high cliff. The driver sounds a horn of frequency $$f$$. The reflected sound heard by the driver has frequency $$2f$$. If v is the velocity of sound, then the velocity of the car, in the same velocity units, will be