Transcript No Slide Title - Mr. Z`s Science Class

Mr. Z’s “Waves” Unit
AIM: What is the Doppler effect?
Describe what is meant by the
Doppler effect
AIM: What is the Doppler effect?
Doppler Effect, phenomenon
AIM: What is the Doppler effect?
A wave is energy,
traveling through a medium.
Waves sometimes reflect, and
sometimes refract. Refraction occurs
because different mediums have
different densities
AIM: What is the Doppler effect?
Have you ever noticed that an
ambulance or a fire truck
always sound louder (or
higher) when it is traveling
towards you as opposed to
traveling away from you.
AIM: What is the Doppler effect?
What is the frequency again?
The number of complete waves
passing a given point in one
second
The greater the frequency the
greater the pitch of a sound
With the Doppler Effect:
The frequency seems to increase to the
observer, but it really does not change
When the source of the waves is moving
towards you, the waves “pile-up”
creating the appearance of an increased
frequency
This apparent change in frequency, is
called the Doppler Effect.
AIM: What is the Doppler effect?
AIM: What is the Doppler effect?
The Doppler effect can be observed to occur
with all types of waves - most notably water
waves, sound waves, and light waves.
We are most familiar with the Doppler effect
because of our experiences with sound waves.
As a police car was traveling towards you with
its siren blasting, the pitch of the siren sound (a
measure of the siren's frequency) was high; and
then suddenly after the car passed by, the pitch
of the siren sound was low.
That was the Doppler effect - an apparent shift
in frequency for a sound wave produced by a
moving source.
AIM: What is the Doppler effect?
AIM: What is the Doppler effect?
The Doppler effect is of interest to astronomers
who use the information about the shift in
frequency of electromagnetic waves produced
by moving stars in order to derive information
about those stars and galaxies.
The belief that the universe is expanding is
based in part upon observations of
electromagnetic waves emitted by stars in
distant galaxies.
Specific information about stars can be
determined by application of the Doppler effect.
Electromagnetic radiation emitted by stars in a
distant galaxy would appear to be shifted
downward in frequency (a "red shift") if the star
is moving away from the Earth.
On the other hand, there is an upward shift in
frequency (a "blue shift") if the star is rotating in
a direction that is towards the Earth.
AIM: What is the Doppler effect?
Because of the Doppler effect, scientists have
been able to determine that the universe is
expanding.
Where else have you heard of the word
“Doppler”?
AIM: What is the Doppler effect?
Who knows what that is?
Doppler Radar:
AIM: What is the Doppler effect?
If the frequency of the
Doppler radar is increasing,
what is that telling you?
The storm is moving towards you!
AIM: What is the Doppler Effect?
Class Activity:
W/S Concepts 7-6
AIM: What is the Doppler Effect?
Homework:
INTERNET QUESTIONS