Optics Answers

An airplane mechanic notices that the sound from a twin-engine aircraft rapidly varies in loudness when both engines are running. What could be causing this vibration from loud to soft?

Assume 2 identical sinusoidal waves are moving through the same medium in the same direction. Under what condition will the amplitude of the resultant wave be greater than either of the 2 original waves?

A. In all cases

B. Only if the waves have no difference in phase

C. Only if the phase difference is less than 90 degrees

D. Only if the phase difference is less than 120 degrees

A train whistle ( f = 400Hz ) sounds higher or lower in frequency depending on whether it approaches or recedes. Calculate this difference for a train moving at a speed of 130km/h . Take the speed of sound in air to be 340m/s

Standing at a crosswalk, you hear a frequency of 560Hz from the siren of an approaching ambulance. After the ambulance passes, the observed frequency of the siren is 480Hz. Determine the ambulance speed from these observations.

(V = 340m/s)

Submarine A travels horizontally at 11.0m/s through ocean water. It emits a sonar signal of frequency f = 5.27 x 10^3 Hz in the forward direction. Submarine B is in front of submarine A and travelling at 3.00m/s relative to the water in the same direction as submarine A. A crewman in submarine B uses his equipment to detect the sound waves ("pings") from submarine A. Determine what is heard by the crewman in submarine B. The speed of sound in water is 1533m/s

A driver travels northbound on a highway at a speed of 25.0m/s. A police car, travelling southbound at a speed of 40.0m/s, approaches with its siren producing sound at a frequency of 2500Hz

(a) What frequency does the driver observe as the police car approaches?

(b) What frequency does the driver detect after the police car passes him?

An ambulance moving at 42m/s sounds its siren whose frequency is 450 Hz. A car is moving in the same direction as the ambulance at 25m/s. What frequency does a person in the car hear;

(a) as the ambulance approached the car?

(b) After the ambulance passes the the car?

[Take v= 340m/s]

The radar systems used by police to detect speeders are sensitive to the Doppler shift of a pulse of microwaves. Explain how sensitivity can be used to measure the speed of a car.

If a 1.00kHz sound source moves at a speed of 50.0m/s toward a listener who moves at a speed of 30.0m/s in a direction away from the source, what is the apparent frequency heard by the listener? The speed of sound in air is 343m/s.

As you travel down the highway in your car, an ambulance approaches you from the rear at a high speed sounding its siren at a frequency of 500Hz . Which statement is correct?

(a) You hear a frequency less than 500Hz

(b) You hear a frequency equal to 500Hz

(c) You hear a frequency greater than

(d) You hear a frequency greater than 500Hz, whereas the ambulance driver hears a frequency lower than 500Hz