The amount of matter in a body is defined as mass, which is a physical quantity that expresses the measure of inertia of a body, determined by the acceleration produced when a force acts on it.
The unit of mass in the International System of Units (SI) is the <u><em>kilogram</em></u>, which was defined for many years from a standard object (the international prototype of the kilogram located at the International Office of Weights and Measures). However, since of May 20, 2019, its definition became linked to Planck's constant
The intensity of the light has no connection with the photoelectric effect.
That's what was so baffling about it before the particle nature of light was suspected ... a match with a blue flame might stimulate the photoelectric effect, but a high-power red searchlight couldn't do it.
