A
sound emitting source moves along a straight line with speed
v relative to an observer at rest. The speed of sound relative
to a medium is c.A
sound emitting source moves along a straight line with speed
v relative to an observer at rest. The speed of sound relative
to a medium is c.
The observer measures the speed of sound emitted by the source as....
a ... c.
b ... c + v.
c ... c - v.
d ... v - c.
A strong wind is blowing in the direction P to Q as shown,
at less than the speed of sound.
A whistle at Q emits sound of frequency f . Which of the following will be true for a listener at point P?
a No sound will be heard.
b The sound heard will have frequency less than f.
c The sound heard will have frequency f.
d The sound heard will have frequency greater than f.
When a train travels towards you sounding its whistle, the
pitch of the sound you hear is different from when the train is
at rest.
This is because ......
a ... the sound waves are traveling faster towards you.
b ... the wavefronts of the sound reaching you are spaced closer together.
c ... the wavefronts of the sound reaching you are spaced further apart.
d .. the sound frequency emitted by the whistle changes with the speed of the train.
A sound source emits a note of constant frequency. An observer
is traveling in a straight line towards the source at constant
speed.
As she approaches the source she will hear a sound that ....
a ... gets higher and higher in frequency.
b ... gets lower and lower in frequency.
c ... is of constant frequency ... but of a frequency that is higher than that of the sound from the source.
d ... is of constant frequency ... but of a frequency that is lower than that of the sound from the source.
A train approaches and passes through a station. During
this period the velocity of the train is constant and the engine
is continuously sounding its whistle. Which one of the following
correctly describes what an observer on the platform will hear?
a A constant frequency as the train is approaching and an increasing frequency as it is passing through the station.
b An increasing frequency as the train is approaching and a decreasing frequency as it is passing through the station.
c A decreasing frequency as the train is approaching and an increasing frequency as it is passing through the station.
d A constant frequency as the train is approaching and a decreasing frequency as it is passing through the station.
The reason that a higher frequency is heard when an observer
is moving towards a sound source in air is that....
a ... the sound wavelength in air decreases.
b ... the speed of sound waves in the air increases.
c ... the listener movement means that more wavefronts are encountered per unit time.
d ... the sound frequency in the air increases.