D1.
A source of sound approaches a stationary observer. The Doppler effect refers to
A. the increase in loudness of the sound.
C. the increase in frequency of the sound.
D2.
D3.
A car with a siren emitting sound at 480 Hz travels towards a stationary observer at 20 ms 1 .
The speed of sound in air is 330 ms 1 . The stationary observer measures the speed of sound as
A. 240 ms 1
B.
310 ms 1
C.
330 ms 1 D.
350 ms 1

A source of sound emits waves of wavelength, period T and speed v when at rest.

The source moves away from a stationary observer at speed V, relative to the observer.
 wavelength of thesound waves, as measured
 by the observer is

The
A.  + vT
D4.

D5.
B. the increase in wavelength of the sound.
D. the increase in relative speed of the sound.
B.  - vT
C.  +VT
D.  - VT
The wavelength of sound from a stationary source as measured by an observer moving towards
the source will …
A.
increase
accelerates
B.
decrease as the observer accelerates
 as the observer

C.
remain constant
D.
be proportional to the speed of the observer
The speed of sound in still air is c. A source of sound moves away from a stationary observer
at speed v. What will be the speed of sound as measured by the observer?
A. c
C. c – v
B. c + v
D. v – c
D6. When a source of sound moves away from a stationary observer the observed ….
A.
C.
D7.
wavelength will decrease
frequency will decrease
B.
D.
frequency will increase
loudness will increase
Sound of a constant frequency f0 is being emitted by a sound source.
An observer travels in the direction shown at a speed of 0.1 v
where v is the speed of sound.
What is the relationship between f0 and the frequency f of observed sound?
A.
f = 1.1f0
B.
f0 < f < 1.1f0
C.
f = 0.9f0
D8. A stationary source of sound emits waves of wavelength λ,
period T and speed V. The source now moves with speed v
in a straight line away from a stationary observer.
What are the wavelength and the speed of the wave as
detected by the observer?
D9.
D.
A
B
C
D
Sound source
f0 > f > 0.9f0
λ
λ – vT
λ
λ + vT
V+v
V
V–v
V
A police car, sounding its siren, is travelling at constant speed towards a stationary observer.
The sound emitted by the siren is of constant frequency. The frequency of the sound as heard by
the observer is higher than that heard by the driver of the police car. The is because the
A.
B.
C.
D.
wavefronts received by the observer are closer together than the wavefronts received by
the driver.
speed of the wavefronts is greater as measured by the observer than by the driver.
speed of the wavefronts is less as measured by the observer than by the driver.
wavefronts received by the observer are further apart than those received by the driver.
10. During a journey an observer travels at constant speed towards,
and then goes beyond, a stationary source of sound of frequency F.
According to the observer the frequency of the sound will
A.
C.
always equal F
always be less than F
B.
D.
always be greater than F
vary throughout the journey
source
D11. The formula ∆𝑓
A. equal to c
=
𝑣
𝑐
f
is only valid when v is
B. almost equal to c C. much less than c
D. greater than c
D12. Light from a galaxy traveling away from us will be observed on earth as having ____________
frequency and _______________ wavelength.
A.
C.
increased, increased
decreased, increased
B.
D.
increased, decreased
decreased, decreased
D13. As a constant light source moves towards you the observed _________and ________ of the
light wave will increase.
A. wavelength , frequency
B.
intensity, wavelength
C.
frequency, intensity
D.
speed, frequency
D14. An observer in a rocket accelerates at high speed towards a stationary star.
The ____________ of the light from the star will be measured to be _______________ .
A.
C.
wavelength, constant
wavelength, decreased
B.
D.
frequency, constant
frequency, decreased
D15. A star emits light at 600 nm. It is observed on earth as having a wavelength of 630 nm.
The star must be travelling _______________ at ______________.
A.
C.
away from us
towards us
0.5c
0.5c
B.
D.
away from us
towards us
0.05c
0.05c
Ultrasound can be used to measure the speed of blood flow in arteries and veins.
D16. Compared to audible sound, ultrasound has _____________ frequency and ____________
wavelength.
A.
increased, increased
B.
increased, decreased
C.
decreased, increased
D.
decreased, decreased
D17. One disadvantage of this technique is that
A.
C.
it is non-invasive
it provides real time results
B.
D.
the beam is not perpendicular to the blood flow
it is potentially carcinogenic
D18. The blood cells shown effectively act as:
I. moving sources
A.
I only
𝜃
II . moving observers
B.
II only
C.
I and II
D.
neither
D19. The detector in the case above will record an increased frequency for _______ red cells.
A.
no
B.
a few
C.
nearly all
D.
all
D20. As 𝜃 increases, the detected wavelength will ________________, and the detected frequency
will _________________.
A.
C.
increase, increase
decrease, increase
B.
D.
increase, decrease
decrease, decrease