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)