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 from the metal

======================= Second Board Section =============================

• Particle Theory: Einsteins Photon Model:
  • Photons carry energy: E = hf     
    • where h = Planck's Constant and f = frequency (color)
• Electron ( e^– ) absorbs energy & gets ejected from metal surface
  • Kinetic energy of ejected electron:
    • hf = K_max + φ,      so
    • K_max = hf – φ      (#1)
      • Note: Label φ as "Work Function" and point to description on graph below
  • Ejected electrons charge capacitor until:
    • K_max = eV_stop      (#2)
  • =========== Split Second Board Section Here ==========
  • Combine #1 and #2, and simplify:

    

    

• Units – electron-volt (eV): Amount of K gained (or lost) by an electron accelerating through an electric potential difference of 1 volts.
  • If V_stop = 5 volts, what is K (in eV)?

======================= Third Board Section =============================

©	St. Lawrence University	Department of Physics

Revised: 12 Jun 24

Canton, NY 13617