A policeman buzzes a whistle of frequency 420 Hz. A car with an audio recorder is moving towards the policeman with a speed of 72 km/h, recording a frequency of . If, after crossing, it records the frequency of , then - is: (Velocity of sound is 300 m/s)
1. Hz
2. 20 Hz
3. 28 Hz
4. 56 Hz
Two organ pipes closed at one end produce \(5\) beats per second in fundamental mode. If the ratio of their lengths is \(10:11\), then their frequencies (in Hz) are:
1. | \(55,50\) | 2. | \(105,100\) |
3. | \(75,70\) | 4. | \(100,95\) |
1. | the pulse is traveling along the negative \(x\text-\)axis. |
2. | the speed of the pulse is \(4\) m/s. |
3. | the amplitude of the pulse is \(5\) m. |
4. | all of these. |
Two wires, \(A\) and \(B,\) of a musical instrument 'Sitar' produce \(3\) beats per second. If the tension of \(B\) is raised, the number of beats becomes \(1\) beat per second. If the frequency of \(A\) is \(450~\text{Hz}\), then the original frequency of \(B\) will be:
1. \(447~\text{Hz}\)
2. \(453~\text{Hz}\)
3. \(449~\text{Hz}\)
4. \(451~\text{Hz}\)
A train moves towards a stationary observer at 50 m/s. The train sounds a whistle and its frequency is registered by the observer as . If the train's speed is increased by 25 m/s, the frequency registered is . If the speed of sound is 300 m/s, then : is:
1. 3:5
2. 5:7
3. 7:9
4. 9:10
1. | \(l\) | 2. | \(2l\) |
3. | \(3l\) | 4. | \(4l\) |
1. | Wavelength of the component waves is \(10~\text{cm}.\) |
2. | The separation between a node and the nearest antinode is \(2.5~\text{cm}.\) |
3. | Frequency of the component wave is \(0.25~\text{Hz}\). |
4. | All of these |