Effect of Potential on Photocurrent
Observation of how the photocurrent varies with the potential difference applied between the emitter and collector electrodes.
What is Effect of Potential on Photocurrent?
The flow of electrons emitted from a photosensitive surface due to incident light, measured as an electric current.
Key formula / rule: Maximum Kinetic Energy
Key points
- Understand the relationship between photocurrent and applied potential.
- Define and identify saturation current.
- Define and identify stopping potential.
- Explain the factors affecting saturation current and stopping potential.
Common exam trap
Confusing stopping potential with saturation potential.
Definitions
- Term
Photocurrent
- Meaning
The flow of electrons emitted from a photosensitive surface due to incident light, measured as an electric current.
- Term
Saturation Current
- Meaning
The maximum photocurrent obtained when all the photoelectrons emitted by the surface are collected by the collector electrode.
- Term
Stopping Potential (Vs)
- Meaning
The minimum negative potential applied to the collector electrode with respect to the emitter, at which the photocurrent becomes zero.
Learning objectives
Understand the relationship between photocurrent and applied potential.
Define and identify saturation current.
Define and identify stopping potential.
Explain the factors affecting saturation current and stopping potential.
Relate stopping potential to the maximum kinetic energy of photoelectrons.
Formulae
- Name
Maximum Kinetic Energy
- Note
Where Kmax is the maximum kinetic energy of the emitted photoelectron, e is the electronic charge, and Vs is the stopping potential.
- Expression
Kmax = eVs
- Name
Einstein's Photoelectric Equation
- Note
Relates the energy of incident photon (hν) to the work function (Φ₀) and the maximum kinetic energy of emitted electrons.
- Expression
hν = Φ₀ + Kmax = Φ₀ + eVs
Prerequisites
Photoelectric effect
Work function
Threshold frequency
Intensity of light
Kinetic energy
Common mistakes
Confusing stopping potential with saturation potential.
Assuming stopping potential depends on light intensity.
Not understanding that saturation current depends on light intensity.
Keywords
Photoelectric effect
Photocurrent
Saturation current
Stopping potential
Work function
Photon energy
Kinetic energy
Intensity of light
Frequency of light
Practice preview
For a given metal, if the frequency of incident light is increased, while keeping the intensity constant, what happens to the stopping potential and the saturation photocurrent?…
medium
In a photoelectric effect experiment, if the frequency of incident light is kept constant but its intensity is increased, the photocurrent will:…
easy
The stopping potential in a photoelectric effect experiment is the potential difference required to:…
easy