If, the pitch of the sound of the source appears to be dropped by \(15\%\) to a moving person, then determine the velocity of motion of the person. Velocity of the sound \(=340\frac{m}{s}\).
Ans: \(v_{o}=51\frac{m}{s}\).
A bus is moving towards a huge wall with a velocity of \(5\frac{m}{s}\). The driver sounds a horn of frequency \(200Hz\). What is the frequency of beats heard by a passenger of the bus, if the speed of sound in air is \(342\frac{m}{s}\).
Ans: \(5.9Hz\).
The wavelength of light coming from a distance galaxy is found to be \(0.5\%\) more than that coming from a source on earth. Calculate: The velocity of the galaxy. Given: \(C=\left(3\times10^{8}\right)\frac{m}{s}\).
A whistle of frequency \(540Hz\) rotates in a circle of radius \(2m\) at an angular speed of \(15\frac{rad}{s}\). What is the lowest and highest frequency heard by a listener a long distance away at rest w.r.t centre of the circle? Can the apparent frequency be ever equal to the actual frequency? take: \(V_{sound}=330\frac{m}{s}\).
Ans: \(\nu_{lowest}=495Hz\) and \(\nu_{highest}=594Hz\).
A policeman on duty detects a drop of \(15\%\) in the pitch of the horn of a motor car as it crosses him. If, the velocity of the sound is \(330\frac{m}{s}\)./ calculate: the speed of the car.
Ans: \(V_{car}=26.75\frac{m}{s}\).
Find: the difference in the apparent frequencies when (i) the source of sound approaches the stationary observer and (ii) the observer is approaching the stationary source. Take: \(b\) as the relative velocity between source and the observer in both case and \(V\) as the velocity of the wave.
Ans: \(\frac{Vb^{2}}{V\left(V-b\right)}\).
The siren of two fire engines have a frequency of \(600Hz\) each. A hears the sirens from the two engines, one approaching him with a speed of \(36\frac{km}{h}\) and the other is going away from him at a speed of \(54\frac{km}{h}\). What is the difference in the frequencies of two siren heard by the man? Take: Speed of sound to be \(340\frac{m}{s}\).
Ans: \(41.6Hz\).
On a quite day, two persons A and B, each sounding a note of frequency \(580Hz\), are standing a few metres apart. calculate: the number of beats heard by each in one second when A moves towards B with a velocity of \(4\frac{m}{s}\). Speed of sound in air \(=330\frac{m}{s}\).
Ans: \(n=7\).
The spectral line for a given element is received from a distant star is shifted towards the longer wavelength by \(0.032\%\). calculate: the velocity of the star in the line of sight.
