The Photoelectric Equation

• What is the formula for the energy of a photon?

  E = hf
• What happens to photons with frequencies above the threshold frequency?

  They have more energy than the work function
• What energy is used to release the photoelectron from the metal?

  An amount equal to the work function
• What happens to the remaining energy after releasing the photoelectron?

  It becomes kinetic energy of the photoelectron
• What is the photoelectric equation?

  hf = Φ + E
• How can the photoelectric equation be expressed in terms of kinetic energy?

  E = hf = Φ + ½ mv
• What does h represent in the photoelectric equation?

  Planck's constant (J s)
• What does f represent in the photoelectric equation?

  The frequency of the incident radiation (Hz)
• What does Φ represent in the photoelectric equation?

  The work function of the material (J)
• What does ½ mv represent in the photoelectric equation?

  The maximum kinetic energy of the photoelectrons (J)
• What does hf equal in terms of photon energy?

  It is the energy of a single photon
• What occurs if the incident photons do not have enough frequency?

  No electrons will be emitted
• What is the threshold frequency in the context of photoelectric emission?

  It is when hf = Φ
• What does the maximum kinetic energy depend on?

  It depends only on the frequency of the photon
• What is the relationship between the number of photoelectrons and the intensity of radiation?

  More photons increase the number of photoelectrons

  
• Why do photoelectrons with maximum kinetic energy come from the surface?

  They require less energy to leave the metal
• What is the photoelectric current a measure of?

  The number of photoelectrons emitted per second
• How is the photoelectric current calculated?

  By multiplying the number of electrons by charge
• What must be the same when using the photoelectric equation?

  hf, Φ, and E must have the same units
• What happens to the photoelectric current if the frequency changes but the number of photons remains constant?

  The photoelectric current remains constant
• What happens to the photoelectric current if the frequency changes while keeping intensity constant?

  The photoelectric current will change
• What does the equation I = P/A represent?

  Intensity is power per unit area
• What does the equation I = nhf represent?

  It accounts for n number of photons
• What happens to the number of photons if frequency increases while intensity remains constant?

  The number of photons must decrease
• Why do fewer photons maintain intensity at higher frequencies?

  Each photon has higher energy at higher frequencies