1. Modern Physics History
Chatfield Senior High, Mr. Boyle

2. J.J. Thompson (1897) Plum pudding model The charge to mass ratio is
e/m=1.76 X C/kg

3. Millikan’s Oil Drop Experiment (1911)
Determined the charge on an electron. 1 e- = 1.6 X Coulomb
The gravitational force matches the electrostatic force with an oil drop

4. Rutherford’s Scattering Experiment (1911)
An alpha particle was sent through gold foil. Most passed straight through but some were largely deflected.

5. Planck’s Quantum Hypothesis (1908)
Photons (packets of light energy) radiating at different frequencies create different energy levels
E = n h f (where h=Planck’s constant=6.626 X J s)

6. Photoelectric effect (1913)
When light shines on a metal surface, electrons are emitted from the surface with regard to frequency of incident light (E=nhf)
If frequency is below a cut-off frequency, there is no transmission

7. Compton Effect (1923)
When an X-ray photon collides with an electron, the collision obeys the conservation of momentum

8. Bohr Model of a Hydrogen Atom (1913)
Studied the hydrogen spectrum to find proof of the energy levels

9. deBroglie Hypothesis (1923)
Extended the wave/particle duality of photons

10. Davisson-Germer Experiment (1923)
Studied electron reflection from a nickel target. They found the wavelength of an electron.

11. Heisenberg Uncertainty Principle (1927)
In any experiment involving properties of an atom you either do not know an object’s speed or position

12. Erwin Schrodinger
Developed probabilistic wave functions describing quantum mechanics
Schrodinger’s cat

13. Einstein ( )
Developed relativity, an offshoot of frames of reference.
Describe behavior of objects when they approached the speed of light
E=mc2
God does not play dice with the universe

14. Paragraph
After you have watched The Elegant Universe, write a paragraph that answers the following.
(a) What do you think is the nature of gravitational force? In your answer compare relativity with quantum physics. *
(b) What do think about string theory? (c) How has your belief about the size of the universe changed since the beginning of the course?