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Flashcards in Light Deck (12)
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1

How does light travel?

Fast. 300,000 kps
Straight - Euclid

2

What did early Greeks think it was?

- came from the eye (fire of Aphrodite)
- a ray - Pythagoras, reflected through prisms
- Euclid - a straight ray, angle of reflection.

3

Newton on light?
Problems?

- corpuscles following prism experiments to disprove Descartes

- if particles, how can two beams cross?

4

Huygens on light?

Problems?

- 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

Young on light. His experiment?

Young - double slit experiment
- interference of light patterns, consistent with waves
- wave lengths explained colours of light

6

What did Michelson Morley prove?

- if ether exists, light should travel more slowly against the flow of it. This doesn't happen.

7

What did Clerk Maxwell find?

- following Faraday. Light is an EM wave.
- light can be bent passing through magnetic field, hence mirages etc.

8

What contribution did hertz make?

- Hertz discovered radio waves, confirming Maxwell's equations.
- it was a certainty that light was a wave.
- some problems remained, eg spectral lines.

9

What did Wollaston note?

- light from the sun seemed to be missing wavelengths. This suggested particles, as they were being absorbed in the atmosphere.

10

What did Einstein do?

- researching the photoelectric effect discovered photons.
- end of wave theory.
- wave/particle duality, a key principle of QT

11

What did de Brolgie do?

- expanded on Einstein's equations.
- frequency of a wave relates to the energy and mass of particles.

12

What is light?

Visible part of EM spectrum
A type of energy