The world of physics is a strange world indeed.At
end of
nineteenth century it was found that a negatively charged metal plate would discharge when illuminated, but a positively charged one would not.
Then it was found by some researchers that NO metal plate would discharge.
Other researchers found that red light had no effect, but blue discharged
plate.
The "photoelectric effect" was a mess.
Max Planck discovered that light consisted of particles. And each particle (or quantum) had an energy that could be defined as Joules.
The science was very simple. Take
frequency of that light particle, multiply by Planck's constant, and you find how many Joules of energy are in that particle.
You could even pretend that this light particle collided with an electric particle -
electron. If so, it would transfer its energy to that electron in just
same way as
chemistry of a battery energises electrons.
So we could define
near infra-red as 1.7 electron volts, and at
other end of
spectrum ultra-violet begins at 3.2.
For this he got
Nobel prize.
With
electron-voltages of light being now defined, Einstein decided to tackle
problem of
metal plate. Why was it that only NEGATIVE electricity would be discharged? Because there is only one kind of "charge-carrier". Or so it seemed at
time.
Why did some researchers find that NO metal plate would discharge? Because
voltages are LOW. Even
slightest film of grease or dirt could INSULATE against less than 3.2 volts.
And why did blue light work when red did not? The answer lay in Planck's electron voltages.
Einstein discovered that
effect varied with
TYPE of metal used for that plate. Each element, sodium, potassium, iron, copper,
noble metals such as platinum &c., had a unique voltage.
That voltage represented
energy that had to be present in
light in order to free
electrons.
That voltage became known as
WORK FUNCTION.
Knowing this, scientists began to research
forces that hold atoms together. In
technical literature, Einstein's name was cited so often that
Nobel Prize Committee could not ignore it.
So Einstein won
Nobel Prize.
It is true that further researches modified
simple model that scientists had used. For example,
particle model of Planck suggested that an ultra-violet "PHOTON" could travel for thousands of millions of years through space, retaining its 3.2 eV energy - and NEVER become two photons at 1.6 eV each.
This is
LAW OF CONSERVATION OF MATTER.
But after that huge journey, it needs only for that photon to hit a suitable crystal and it does indeed divide. You get TWO photons for
price of ONE. This is only possible if
photon consists of NOTHING.
So
wave model of light began to supervene. Waves consist of nothing but a pattern. And questions were asked as to whether there is a SUBSTANCE in which
waves are formed. Does space consist of aether?