Higher Physics - Unit 3 - Photoelectric Effect and Photons

I created my own revision notes for all units of the Higher Physics course.

These are revision notes for part of the 3rd unit (Radiation and Matter), section 3 (Optoelectronics and Semi-conductors). I've uploaded all the subsections of this section in different files as they are otherwise too large.

Photoelectric Effect and Photons covers:
• Meaning of the photoelectric effect
• Experiment to show the photoelectric effect
• Conditions for photoelectric effect to work
• What the work function is
• Further information on the work function
• Light is a photon
• What a photon is
• Properties of a photon
• Photon equations

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  • Created by: Visser
  • Created on: 08-05-10 16:29
Preview of Higher Physics - Unit 3 - Photoelectric Effect and Photons

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PHOTOELECTRIC EFFECT
When certain metals are exposed to the correct frequency of electromagnetic radiation, electrons are ejected from the
surface. The interaction between light and electrons is called the photoelectric effect.
Evacuated tube ­ so the photoelectrons don't collide with air atoms
Quartz window ­ glass absorbs UV radiation
UV strikes the zinc cathode, causing electrons (photoelectrons) to be emitted (from the surface of the zinc)
Photoelectrons are repelled by the cathode and attracted o the anode ­ thus a current (which is measured by the
ammeter) flows ­ this is the photoelectric current
Clean +charge zinc plate ­ exposed to intense white light = no discharge
Clean ­charge zinc plate ­ exposed to intense white light = no discharge
Clean +charge zinc plate ­ exposed to ultraviolet source = no discharge
Clean ­charge zinc plate ­ exposed to ultraviolet source = discharge

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­ the
photoelectric current produced is directly proportional to the intensity of the radiation at the surface
WORK FUNCTION
The work function is the minimum energy required to remove
an electron from a metal.
Different metals have different work functions.
Lower W = lower = easier to remove electrons.
Higher W = higher = harder to remove electrons.…read more

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Max kinetic energy = energy of photon ­ work function:
If N photons per second are incident per unit area on a surface, the intensity at the surface is:…read more

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