1. Light
Ken Rogers
Miami Killian

2. Electrons move about the nucleus in energy levels.
3rd Energy Level
2nd Energy Level
1st Energy Level
1st
2nd
3rd

3. These energy levels surround the nucleus of the atom.

4. The electron absorbs energy and moves to a higher energy level.
When energy is added to an atom, it causes electrons to move further away from the nucleus where the electrons have more energy. This step is called
absorption.
Energy level 3
The electron absorbs energy and moves to a higher energy level.
energy level 2
energy level 1

5. When the electron falls back down to a lower energy level, the electron loses the energy it previously absorbed.
This step (where the electron gives back its absorbed energy) is called
emission.
Energy level 3
It emits this energy in the form of a photon of light or radiant energy.
energy level 2
energy level 1

6. Electromagnetic waves are produced by the movement of electrons within the atom. These waves are also called "electromagnetic radiation" because they radiate from the electrically charged particles. They travel through empty space as well as through air and other substances.

7. Scientists have observed that electromagnetic radiation has a dual "personality."
Besides acting like waves, it acts like a stream of particles (called "photons") that have no mass.
The photons with the highest energy correspond to the shortest wavelengths.

8. a) longer wavelength b) shorter wavelength

9. Measuring wavelength the distance from peak to peak or trough to trough is one way scientists measure the length of a wave.
lambda
peak to peak l
trough to trough l

10. Electromagnetic Spectrum
Visible
Microwave
X-Rays IR
Gamma Rays UV
Radio
400 nm
700 nm

11. Electromagnetic Spectrum
Wavelength in meters
– – x10-7-4x x –
Radio
Microwave
Infrared
Visible
Ultraviolet
X-Ray
Gamma Ray
About the size of:
Grains of sugar
Protozoans
Bacteria
Molecules
Atoms
Atomic nuclei
Buildings

12. wavelength, l = the distance between similar parts of the waves
frequency (f or n) = the number of waves per second
(also called Hertz or cycles per second)
as the wavelength gets smaller (more crowded together) the frequency (# of waves) gets larger.

13. Count the number of waves that go by.
To see that relationship, watch as we race these two light waves pass the red line.
Count the number of waves that go by.
The shorter the wavelength, the higher the frequency. l 8
The greater the wavelength, the lower the frequency. l 3

14. This is an inverse proportion which is equal to a constant.
The equation is:
wavelength times frequency equals a constant or
l . f = c
the value of the constant, c is 3.00 x 108 m/s
and is the speed of light.
so, l . f = 3.00 x 108 m/s

15. Example:
All FM radio stations broadcast in megaHertz (1 x 106 waves/s).
Coast FM, 97.3 on the FM dial, broadcasts 97.3 megaHertz or
97.3 x 106/s.
What is the wavelength (distance between waves) for this frequency of radio waves?
l . f = c
l . f = 3.00 x 108 m/s
l x 106/s = 3.00 x 108 m/s
l = x 108 m/s
97.3 x 106/s
= m

16. The energy that a photon of light possesses
is a function of (depends on) its frequency.
The more waves light has, the more energy it has.
Or, the higher the frequency, the higher the energy.
This is a direct proportion.
The equation is:
Energy of light = h . f or E = h . f
where h (Planck’s constant) is 6.63 x joule . s

17. Example:
What is the energy of a single photon of X-ray which has a frequency of 2.00 x 1018/s?
E = h . f
E = 6.63 x joule . s . f
E = 6.63 x J . s x 1018/s
E= 1.33 x J (per photon)

18. Bright line emission spectrum for hydrogen
Bright line emission spectrum for sodium
Link

19. Emission spectrum of hydrogen
Hydrogen gas in glass tube
Glass Prism