Light, Waves or Particles?

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What did the photo-electric effect show in the 19th century?
Light only acts as a particle.
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What did Max Planck find EM waves can only travel as?
Quanta, or quantum for one packet.
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What was his formula?
E=hf
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What are units of Planck's constant?
Js
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If energy is higher, how come this is?
The frequency of photons is higher.
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What did Einstein suggest faces and energy in EM waves can exist as?
Photons
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Einstein suggested that particles could either transfer all energy or...
No energy,
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Photons have no charge, so they are...
Neutral
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Why are eV used?
Joules are tiny when measuring energy.
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When is eV transferred to kinetic energy?
When an electron is accelerated between two electrodes. Hence eV=1/2mv2
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What is the formula for eV?
eV = e*V
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What are voltage units?
JV^-1
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Describe basic steps of an LED experiment?
1. Connect an LED of known wavelength, 2. Close black out blinds and apply shaded tube so no light exposes LED, 3. Adjust variable power supply until current begins to flow, and record V0 - threshold voltage. On a V-f graph, find gradient V/F*e=h
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Other cards in this set

Card 2

Front

What did Max Planck find EM waves can only travel as?

Back

Quanta, or quantum for one packet.

Card 3

Front

What was his formula?

Back

Preview of the front of card 3

Card 4

Front

What are units of Planck's constant?

Back

Preview of the front of card 4

Card 5

Front

If energy is higher, how come this is?

Back

Preview of the front of card 5
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