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Slide 1

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OCR PHYSICS A UNIT 2…read more

Slide 2

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Energy of a Photon
· Photon
· a quantum of EM radiation
· E = hf
· E = energy of a photon/J
· h = Plank's constant (6.63x10-34Js)
· f = frequency/Hz…read more

Slide 3

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Electron Volts
· eV = a unit of energy
· 1eV = 1.6x10-19J
· electron volt = the kinetic energy
gained by an electron when it is
accelerated through a pd of 1V.
· eV = ½ mv2…read more

Slide 4

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Experiment Measuring
Planck's Constant
1. Connect an LED of known wavelength in the
electrical circuit shown.
2. Start off with no current flowing through
the circuit, then adjust the variable resistor
until a current begins to flow.
3. Record the voltage (V0) across the LED & the
wavelength of light being emitted.
4. Repeat with LEDs of different wavelengths.
5. Plot a graph of V0 against 1/.
6. You should get a straight line with a
gradient hc/e. Use this to find h.…read more

Slide 5

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The Photoelectric
If you shine light of a high enough
frequency onto the surface of a metal it
will emit electrons.
This is the photoelectric effect.…read more

Slide 6

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Experiments show that:
1. Increasing intensity increased number of
photoelectrons emitted.
2. For a light below a certain threshold
frequency, no electrons are emitted.
3. The maximum kinetic energy of the
photoelectrons increases with frequency,
but is unaffected by the intensity.…read more

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Slide 10

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