1. Have you ever wondered how you get different colored fireworks?
Have you ever wondered how scientists know what stars are made of?

2. Bohr Model, Quantum Mechanics and the Electromagnetic Spectrum
Let’s start with the basics!

3. I. Wave-Particle Duality
Light behaves as both waves and particles
Did you know light was made of particles?

4. A. Light as Waves Basic wave terminology
Wavelength (λ, lambda): Distance between two crests of a wave.
Measured in meters (m)
Frequency (ѵ, nu): Number of wave cycles that pass a given point per second
Measured in hertz, Hz. 1 Hz = 1/s = s-1
Amplitude: Height of wave

6. What is the relationship between wavelength and frequency?
They are inversely proportional.
↑ ѵ, ↓ λ (increase frequency, decrease wavelength)
↓ ѵ, ↑ λ , (decrease frequency, increase wavelength)

7. The Electromagnetic Spectrum
↑ wavelength ↓ wavelength
↓ frequency ↑ frequency
↓energy ↑ energy

8. The Electromagnetic Spectrum
Write in order from longest to shortest wavelength:
radio, microwaves, radar, infrared, visible, ultraviolet, x-rays, gamma rays
Write in order from highest to lowest frequency
Gamma rays, x-rays, ultraviolet, visible, infrared, radar, microwaves, radio

9. B. Light as particles
Energy is quantized – comes in discreet packets or quantities
A quantum (particle) of light is called a photon

10. Putting it all together….seeing the light!

11. C. Bohr Model and the Electromagnetic Spectrum
Let’s talk electrons again….

12. Ground state: Electron is occupying the lowest energy level possible
Excited state: Electron is in a higher energy level than the ground state

13. How does an electron get excited (move up energy levels)?
It must absorb a very specific amount (quantum) of energy.
Where does that energy come from?
Apply electricity
Apply electromagnetic radiation (UV, light, x-ray, etc). EM radiation comes in photons, or packets of energy.

14. How it works…I see the light
Electron in ground state
Electron absorbs photons with a very specific amount of energy
Energy causes electron to move to higher energy level
Electron now in excited state
Excited state = unstable atom
Electron quickly falls back to ground state, emitting photon with same energy it originally absorbed.
Wavelength/frequency of photon may be in visible spectrum
If in visible spectrum, we will see corresponding colors

16. D. Emission and Absorption Spectra
Emission Spectra
Shows the wavelengths emitted by photons as electrons drop down to a lower energy level from a higher energy level (excited state)
Every element has a unique emission spectrum—like a fingerprint.

17. Absorption Spectra
Produced by atom absorbing photons of a specific wavelength

18. Why do Elements have Different Emission/Absorption Spectra?
All atoms have energy levels, but the energy levels of each atom are different distances apart
Different distances = different energies
This means electrons of different atoms must absorb/emit photons of specific, but different energies to move up or down energy levels, so the absorption and emission spectra will be unique to each element.

19. Flame Test

20. http://video. google. com/videoplay