The Photoelectric Effect
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Transcript of The Photoelectric Effect
The Photoelectric Effect
Key Points
What is it ?
• Electrons are emitted from zinc when ultraviolet radiation shines on it.
• Other metals emit electrons with other kinds of radiation.
Why was it a problem ?
• If the frequency of the radiation was reduced below the Threshold Frequency (fo), no electrons were emitted.
• No-one could explain this using wave theory.
What did Einstein say ?
• We must think of light as a particle and not as a wave.
• Each particle carries energy given by E=hf where h is Planck’s Constant.
• There is a certain minimum energy needed to release an electron – called the Work Function given by W=hfo.
Equations
• To release an electron, hf > hfo.
• If hf < hfo, no electrons will be released.
• The kinetic energy of the released electrons is given by Ek = hf – hfo.