Photoelectric Effect and Albert Einstein

Photoelectric effect
Light bombards the surface of a metal and electrons are ejected

Minimum must be met or no action! Once minimum is met, intensity increases rate of ejection.

massless particle of light

Does a photon have mass?
Yes! In 1922 Arthur Compton performed experiments involving collisions of x-rays and electrons that showed photons do exhibit apparent mass.

Energy is quantized
Energy can occur only in discrete units called quanta
EM radiation exhibits wave and particle properties
This phenomenon is known as the dual nature of light.