Light Flashcards
1
Q
How does light travel?
A
Fast. 300,000 kps
Straight - Euclid
2
Q
What did early Greeks think it was?
A
- came from the eye (fire of Aphrodite)
- a ray - Pythagoras, reflected through prisms
- Euclid - a straight ray, angle of reflection.
3
Q
Newton on light?
Problems?
A
- corpuscles following prism experiments to disprove Descartes
- if particles, how can two beams cross?
4
Q
Huygens on light?
Problems?
A
- light must be waves as shadows are diffused.
- transverse waves account for diffusion in crystals
- waves need to travel through a medium.
- ether invented
5
Q
Young on light. His experiment?
A
Young - double slit experiment
- interference of light patterns, consistent with waves
- wave lengths explained colours of light
6
Q
What did Michelson Morley prove?
A
- if ether exists, light should travel more slowly against the flow of it. This doesn’t happen.
7
Q
What did Clerk Maxwell find?
A
- following Faraday. Light is an EM wave.
- light can be bent passing through magnetic field, hence mirages etc.
8
Q
What contribution did hertz make?
A
- Hertz discovered radio waves, confirming Maxwell’s equations.
- it was a certainty that light was a wave.
- some problems remained, eg spectral lines.
9
Q
What did Wollaston note?
A
- light from the sun seemed to be missing wavelengths. This suggested particles, as they were being absorbed in the atmosphere.
10
Q
What did Einstein do?
A
- researching the photoelectric effect discovered photons.
- end of wave theory.
- wave/particle duality, a key principle of QT
11
Q
What did de Brolgie do?
A
- expanded on Einstein’s equations.
- frequency of a wave relates to the energy and mass of particles.
12
Q
What is light?
A
Visible part of EM spectrum
A type of energy
