1. Emission Spectra
Be sure you have something warm to wear, we may go outside for a few minutes later on if there’s time
(sticker)
1. What color of visible light has the shortest wavelengths?
2. What color of visible light has the longest wavelengths?
3. If an atom burns orange, are its excited electrons mostly making big jumps or little jumps?

2. Homework
None

3. Objectives
Be able to explain the Doppler Effect as it relates to light
Be able to explain what redshift indicates about the Big Bang and the present universe

4. Emission Spectrum
Because every element has a unique number, pattern, and arrangement of electrons, every element gives off photons of different wavelengths when it absorbs energy.
Emission spectrum: The individual colors of light emitted by an element when it absorbs energy.
Every element has its own “light fingerprint.”

5. Emission Spectrum
A flame test can’t show you the wavelengths of each photon given off by an element, it shows you the combined effect of all of them put together.

6. Emission Spectra
A tool called a spectroscope works kind of like a prism: it can take light, and isolate each individual wavelength.
If a flame appears orange, for instance, a spectroscope may show that it looks that it looks that way because the element is emitting some red and some yellow, or that the element is just emitting orange, or some combination.

7. Emission Spectra
Bright Line Spectrum = The individual colors of light photons emitted by an energized element.

8. Bright Line Spectra

9. Spectrum Analysis Analyze real spectra:

10. Redshift
When scientists began using this tool to study stars, they noticed something weird.
The fingerprints were there for every star, but they were shifted slightly towards the low frequency (red) end.

11. Redshift
Redshift = The phenomenon in which star emission spectra appear “shifted” towards the red end from where they would normally be

12. Redshift
Redshift was one of the big clues that confirmed the existence of the Big Bang…

13. Big Bang Theory First things first…
Big Bang Theory = Explains that the universe expanded from a hot primordial condition, and is still expanding today.

14. Big Bang Theory
The redshift phenomenon is due to the continued expansion of the universe, and explained by the Doppler Effect.

15. Doppler Effect
Demo

16. Redshift & Big Bang http://www.youtube.com/watch?v=Man9ulEYSgk
The Doppler Effect = the change in frequency & wavelength of a wave for an observer who is moving relative to the wave’s source.

17. Doppler Effect
As the car moved towards you, the horn sounded higher because the sound waves were coming closer together (higher frequency).
As the car moved away, the horn sounded lower in pitch, because the waves were farther apart due to the movement.
If a light is moving towards you, what is happening to its waves?

18. Doppler Effect
An object moving towards you appears more blue/purple than it should.
An object moving away from you appears more red than it should, due to the Doppler Effect.

19. Big Bang
If all these other parts of the universe are redshifted, which direction are they moving relative to us?

20. Big Bang
If all these other parts of the universe are redshifted, which direction are they moving relative to us?
Away! Showing that the universe is expanding.

21. Big Bang
The redshift phenomenon is one of the most famous confirmations of the Big Bang and expanding universe.
Draw a diagram showing a star moving away from Earth, and what’s happening to its light waves because of that.

23. Doppler Effect
Review: Doppler Effect
Review: Big Bang Theory

24. Doppler Effect
Now that you know something about electromagnetic waves and the Doppler Effect, the other major confirmation of the Big Bang - cosmic microwave background radiation - will make more sense.

25. Doppler Effect
As the universe expands, the light of the initial expansion event (Big Bang) is expanded with it.
What kinds of electromagnetic waves have wavelengths longer than light?

26. Cosmic Microwave Background Radiation
As the universe has expanded, the “first lights” have been stretched out, from visible light into microwaves = cosmic microwave background radiation.