1. Emission Spectrum Animation

2. Light and Energy c = f Energy = hf
Particles (photons) and waves at the same time!
c = f
The greater f (frequency), the smaller  (wavelength)
The greater f, the higher the energy of the EM radiation.
Energy = hf
h is Plank’s Constant = x10-34Js

3. Light and Energy
The electromagnetic spectrum

4. Energy and Frequency
The higher the frequency, the greater the energy

5. Which has higher energy – red or blue light?

6. Emission spectra known for hundreds of years
Niels Bohr suggests a reason – energy levels
Electrons orbiting in shells around the nucleus
Energy levels differ from one another

7. Electrons and Light
When an atom absorbs energy, electrons are promoted to higher energy levels.
When the atom releases the absorbed energy, the electron falls back down to lower energy levels and EM radiation is given off (sometimes light)

8. “Too many photons for love, too much electromagnetic radiation…”
© Copyright Michael Offutt 1988

9. Too Many Photons for Love
I went to a dance and saw her standing in the light. She was so beautiful, I knew I had to meet her. She had this look of intelligence and poise. So, I figured out a novel way to greet her. I just walked up and said… There’s just too many photons for love. Too much visible electromagnetic radiation. Too many photons for love, Too much subatomic excitation

10. I said now, so many people thought, That light was just a wave
I said now, so many people thought, That light was just a wave. And of course there were your usual particle fanatics. But the way that light behaved made it clear to all They did something more than classical mechanics. So they figured out that maybe light was like a combo, Bundles of energy that dance away the mambo. But it’s almost midnight and this party’s getting stale. Let’s find someplace dark, And I’ll complete this quantum tale.

11. So we went to my place and sat and talked beside the fire, About how atoms give off photons, When electrons make transitions, Jumping from high levels down to lower ones, Resulting in colourful emissions. And as the fire flickered low, I kept on relating how the world was filled with atoms, With electrons resonating. Absorbing and emitting photons to disclose, The beauty of a leaf, the colour of a rose.

12. There are only certain possibilities
Electrons can only exist at discrete energy levels (these are called orbitals)
Therefore, in changing levels, only certain amounts of energy can be released
These amounts are unique to every element

13. Emission Spectra are Unique
Visit the website and click on any element to see its unique emission and absorption spectra.

14. How are the lines of the line spectrum formed?

15. Spectrum Excited State UV Excited State Excited State IR Ground State
Excited State unstable and drops back down
Excited State
Vi s ible
But only as far as n = 2 this time
n=2
Energy released as a photon
Frequency proportional to energy drop IR
n=1
Ground State

16. Summary Electron normally in Ground State
Energy supplied [ as heat or electricity]
Electron jumps to higher energy level
Now in Excited State
Unstable
Drops back to a lower level

17. Energy that was absorbed to make the jump up is now released as a photon
Frequency depends on difference in energy levels [ E2 - E1 = hf ] h is Plank’s Constant and f is frequency of light
When electron falls to
n = 1 level gives UV Range
n = 2 level gives Visible Range
n = 3,4 or 5 levels gives IR Range