Meet Albert Einstein
the physicist behind this idea

B) Einstein explains photoelectric effect

1) Light intensity and electron emission explained.

Photons are received individually
Each photon emits e -
Light emitted as particles (quanta of light - photon)

Brightness (Intensity) - measure of # of photons emitted.

Frequency measure of energy of light
 

Photon Energy = 5 eV	KE = 2 eV

**eV - electron volts - unit of energy

How much work did this photon have to do to remove the electron? 

Answer: 3 eV

What would happen if a photon
 of 2 eV hit the same metal?

Photon Energy = 5 eV	KE = 2 eV

Photon would not have enough energy to emit an electron

Photon Energy = 5 eV	KE = 2 eV

E_max = hf - W_o