# The Photon Model

- Created by: theninjaemu
- Created on: 07-04-17 10:12

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- The Photon Model
- Photons
- The smallest undividable packet of light
- Packets of energy rather than a wave
- Used to explain how EM radiation interacts with matter
- Can explain the wave model and its propagation through space

- Photon energy
- The energy of a photon is directly proportional to its frequency
- E=hf
- E is the energy in J, F is the frequency in Hz, h is the Planck Constant

- Combined with f= c/wavelength, you can get to E= hc/wavelength
- The energy of a photon is inversely proportional to its wavelength

- The energy of a photon is directly proportional to its frequency
- Questions of scale
- 1 electron volt (1eV) is the energy transferred to or from an electron when it passes through a p.d. of 1 volt
- 1eV is equivalent to 1.6x10^-19 J
- 1J is equivalent to 6.25x10^18 eV
- Work done on an electron as it moves across a p.d. of 1V is the p.d. x the charge on the electron
- W=VQ
- W=Ve

- LEDs and the Planck constant (h)
- An experiment can be done to determine a value for h using LEDs
- LEDs emit visible photons when the p.d. across them reaches a critical value (threshold p.d.)
- When this is reached, the LED emits photons of a specific wavelength
- At threshold p.d, the energy transfered is aproximately equal to the energy of the photon it emits, so Ve=hf
- Plotting a graph of V against 1/wavelength means h can be calculated by finding the gradient

- Photons

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