REVISION SOUND
Jan 19, 2016
REVISIONSOUND
DOPPLER EFFECT• Doppler effect as the change in frequency (or
pitch) of the sound detected by a listener because the sound source and the listener
have different velocities relative to the medium of sound propagation
𝑓 𝐿=𝑣±𝑣 𝐿
𝑣±𝑣𝑆
𝑓 𝑆
FORMULA
𝑓 𝐿=𝑣±𝑣 𝐿
𝑣±𝑣𝑆
𝑓 𝑆Frequenc
y of listener
Frequency of
sourceSpeed of source
Speed of listener
Speed of sound in medium
Speed of sound in medium
f
APAR
T
𝑓 𝐿=𝑣±𝑣 𝐿
𝑣±𝑣𝑆
𝑓 𝑆+-
f
TOW
ARD EACH
OTH
ER
𝑓 𝐿=𝑣±𝑣 𝐿
𝑣±𝑣𝑆
𝑓 𝑆+-
ELECTROMAGNETIC SPECTRUM
light wavesIt does NOT need a medium to propagate
It consists of seven main groups
DOPPLER EFFECT with LIGHT
DOPPLER EFFECT with LIGHT
DOPPLER EFFECT with LIGHT
DOPPLER EFFECT with LIGHT
-1
Dolphins use ultrasonic waves to explore their surroundings.
When a dolphin is 100m from a rock, it emits an ultrasonic wave
with a frequency of 250 kHz,
while swimming at 20m.s towards the rock.
Assu
-1
.
a Calculate the frequency of the sound waves that reach the rock
b When the dolphin is 50m from the rock, i
me that the speed of sound
t emits another wave
of 25
in water is
0 kHz .
How do
1500m.
es
s .
this preceived frequency relate to the answer is a)
GENERAL DOPPLER EFFECT
The siren of a stationary ambulance emits ound
with a frequency of 700 Hz.
The driver of a car approaches the ambulance and
then passes it by. He perceives that the frequency
of the siren changes by
s
-1
a Name and state the wave phenomena
b Take the speed of sound in air as 340m.s and
calculate the speed of the car when it passes
the ambul
80Hz
ance
CHANGES IN FREQUENCY
a)
b)