The Photoelectric Effect
BlackBoard Notes
======================= Photo - Click for a Larger Version =============================
======================= First Board Section =============================
- Is this experiment explained by particle (photon) theory, or by wave theory?
- Inside the photoelectric head:
- Electrons ( e– ) absorb energy and can be ejected
======================= Second Board Section =============================
- Particle Theory: Einsteins Photon Model:
- Photons carry energy:
E = hf (where h = Planck's Constant)
- Electron ( e– ) absorbs energy & gets ejected from metal surface
- Kinetic energy of ejected electron:
- hf = Kmax + φ, so
- Kmax = hf – φ (#1)
- Note: Label φ as "Work Function" and point to description on graph below
- Ejected electrons charge capacitor until:
- =========== Split Second Board Section Here ==========
- Combine #1 and #2, and simplify:
- Units – electron-volt (eV): Amount of KE gained (or lost) by an electron accelerating through an electric potential difference of 1 volts.
- If Vstop = 5 volts, what is K (in eV)?
======================= Third Board Section =============================
Wave theory:
- Kmax depends on light intensity (brighter light → greater ejected energy)
- Use "Relative transmission" slide
- Regions with 20%, 40%, 60%, 80% and 100% transmission
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Revised: 30 May 23
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Canton, NY 13617
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