Then what could be done to increase the energy of each incident
light particle, so that the electrons emitted by collision had more
The answer was that the speed of the outgoing electrons depended
on the frequency of light used.
The higher the frequency, the faster the electrons moved (right).
The ejected electrons behaved as if the energy (E) of the incoming
particles of light was directly proportional to the light frequency:
or E = h,
in which h is a constant.