In the photoelectric effect, the threshold frequency is the minimum frequency of light needed to emit electrons from a material.
- If the light’s frequency is below the threshold, no electrons are emitted, no matter how intense the light is.
- If the light’s frequency is equal to or above the threshold, electrons are emitted. The higher the frequency above the threshold, the more kinetic energy the emitted electrons have.
- The threshold frequency depends on the material, because different materials have different work functions (the energy needed for electrons to escape).
Key idea: The threshold frequency sets the cutoff point—light must be at least this frequent to produce photoelectrons.