Doppler effect for senior high school (light of star)

Doppler effect power point slide for senior high students

1. The Origin and Nature of Light
•Celebration of Knowledge #2 (aka Exam #2)
is Thursday March 8th in N210
•Tailgate Party (aka exam review) is
Wednesday March 7th in N210 from 4-6pm
•HW #5–Handed out in class Feb 27th on the topic
of Luminosity Area and Temperature, and Due IN-
CLASS Tuesday March 6th

2. The Origin and Nature of Light
•HW#6–Masteringastronomy online homework
on Properties of Light and Matter.
Available March 1
st
, Due March 8
th
by 10am.

3. What physical situation makes
this spectrum?

4. What can we learn by
analyzing starlight?
•A star’s temperature
•A star’s chemical composition
-peak wavelength of the spectral curve
-dips in the spectral curve or the
lines in the absorption spectrum
•A star’s motion

5. The Doppler Effect
•Definition:“The change in wavelength of
radiation (light) due to the relative motion
between the source and the observer along
the line of sight.”

6. Astronomers use the Doppler Effect to learn
about the radial(along the line of sight) motions
of stars, and other astronomical objects.

7. Real Life Examples of Doppler
Effect
•Doppler Radar (for weather)
•Airplane radar system
•Submarine radar system
–Ok, anything with radar
•Radar gun, used by Law Enforcement
Officers…

8. The Doppler Effect
•Definition:“The change in wavelength of
radiation (light) due to the relative
motion between the source and the
observeralong the line of sight.”

9. Doppler Effect
•When something which is giving off light moves
towards or awayfrom you, the wavelength of the
emitted light is changed or shifted
V=0

10. Doppler Effect
•When the source of light is moving away from the
observer the wavelength of the emitted light will
appear to increase. We call this a “redshift”.

11. Doppler Effect
•When the source of light is moving towards the
observer the wavelength of the emitted light will
appear to decrease. We call this a “blueshift”.

12. The Doppler Effect
•Definition: “The change in wavelength of
radiation due to relative motion between the
source and the observer along the line of
sight.”

13. Doppler Effect
•“Along the line of sight” means the Doppler
Effect happens only if the object which is
emitting light is moving towardsyou or
away fromyou.
–An object moving “side to side” or
perpendicular, relative to your line of sight,
will notexperience a Doppler Effect.

14. Astronomy Application
V=0

15. Doppler Shifts
•Redshift (to longer wavelengths): The source is
moving awayfromthe observer
•Blueshift (to shorter wavelengths): The source is
moving towardsthe observer
Dl= wavelength shift
l
o= wavelength if source is not moving
v = velocity of source
c= speed of lightc
v
0

l
lD

16. What can we learn by
analyzing starlight?
•A star’s temperature
•A star’s chemical composition
-peak wavelength of the spectral curve
-dips in the spectral curve or the
lines in the absorption spectrum
•A star’s motion
-Doppler shift

17. Doppler Shift
Lecture Tutorial Handout
•Work with a partner!
•Read the instructions and questions carefully.
•Discuss the concepts and your answers with one
another. Take time to understand it now!!!!
•Come to a consensus answer you both agree on and
write complete thoughts into your LT.
•If you get stuck or are not sure of your answer, ask
another group.

18. The Doppler Effect causes light
from a source moving away to:
1.be shifted to shorter wavelengths.
2.be shifted to longer wavelengths.
3.changes in velocity.
4.Both a and c above
5.Both b and c above

19. You observe two spectra (shown below) that are redshifted
relative to that of a stationary source of light. Which of the
following statements best describes how the sources of light
that produced the two spectra were moving?
BLUE RED
Spectrum A
Spectrum B
1.Source A is moving faster than source B.
2.Source B is moving faster than source A.
3.Both sources are moving with the same speed.
4.It is impossible to tell from looking at these spectra.

20. A bright star is moving toward Earth. If you
were to look at the spectrum of this star, what
would it look like?
1.an absorption spectrum that is redshifted relative to an unmoving star
2.an emission spectrum that is redshifted relative to an unmoving star
3.a continuous spectrum that is blueshifted relative to an unmoving star
4.an absorption spectrum that is blueshifted relative to an unmoving star
5.a continuous spectrum that is redshifted relative to an unmoving star