Photoelectric effect
The key idea
In the photoelectric effect, electrons are emitted from a material when incident electromagnetic radiation has sufficiently high photon energy.
Why it matters
Increasing intensity raises the number of available photons, but below the threshold frequency it does not compensate for insufficient photon energy.
A picture to remember
Increasing intensity raises the number of available photons, but below the threshold frequency it does not compensate for insufficient photon energy.