In 1900,
a German scientist named Max Planck wrote an equation to
show this the relationship between energy and frequency
of electromagnetic radiation :

E
= hn

where E
is the energy of a bit of light called a quantum,
A quantum is the smallest bit of electromagnetic
radiation that can be emitted.It is also called a photon
of light or small “packet” of electromagnetic
radiation.The “h” in the above equation is a very small
constant called “Planck’s constant” (6.626068 ×
10^{-34} J s) and “n”
is the frequency of the radiation.Through various experiments of Planck and Albert
Einstein, it came to be accepted that light has
properties of particles as well as waves.Planck’s “quantum” idea became the basis
for the modern understanding of atomic structure.In the above equation, as the frequency of
radiation increases, its energy increases by the
increment “h”.In other words, energy was not continuous, it was
quantized
– only certain energies are allowed.Continuous energy and quantized energy can be
likened to aramp
versus a set of stairs connecting two levels of a
building.The
ramp is analogous to continuous energy – you can sit
at any position along the ramp and thus be at any
elevation between the two levels.The stairs are analogous to quantized or discrete
energy – you can only sit at certain elevations
between the two levels and nowhere in between.You may sit only on the steps, not in between the
steps.Only
certain elevations are allowed.