184.108.40.206 After this until late 19th Century
mechanics became a discipline capable
of describing the motion of particles in
a clear and deterministic way.
220.127.116.11.1 (Light / Opticks was a
stream of particles -
1.2 James Clerk Maxwell
1.2.1 1873 - Treatise on
18.104.22.168 He determined, that all
electromagnetism was linked,
and that the speed of light
could be determined
1.2.2 Hans Christian
Oersted / Michael
1.3 Thomas Young
22.214.171.124 Light had
126.96.36.199.1 Interference Phenomena
188.8.131.52.1.1 "Adding in phase waves
reinforcement - Adding
out of phase waves
2 The OLD Quantum Theory
2.1 Michelson and Morley 1880
184.108.40.206.1 Discovered that the
spectrum of Hydrogen,
could be described by a
simple mathematical formula
when light is shone through hydrogen gas, and then through a prism, the frequencies that have been absorbed by the gas are absent in the spectra. These frequencies could be predicted by a certain simple formula.
2.2.2 J.J Thomson
220.127.116.11.1 Was the first to discover Electrons
18.104.22.168.1.1 In his model of the Atom -
Electrons, Neutrons and Protons.
His model was unsuccessful in
explaining Balmer's results
22.214.171.124 Tried to
2.3 The UltraViolet Catastrophe
2.3.1 Lord Rayleigh
126.96.36.199.1 James Clerk Maxwell &
Ludwig Bolzmann concluded
that they cold reliably predict
the overall behaviour of a
188.8.131.52.1.1 Lord Rayleigh used this
'statistical physics' applied
to a case of the black body
A black body is a hypothetical, whereby this 'body' can totally absorb all the radiation emitted at it, and then re-emit it, when it is being recorded.
In this assumption, a good approximtion could be made to a specially prepared oven. In doing so the answer is only dependant on the temperature of the black body.
184.108.40.206.1.1.1 The results from the Black
body experiment did not
match the calculations
220.127.116.11.18.104.22.168 Classical physics assumed
that radiation 'oozed' in and
out of the 'black body'
2.3.2 Max Planck
22.214.171.124 Submitted that energy was emitted or
absorbed from time to time in small
packets of energy of a definite size and
that the size of this energy packet was
directly proportional to the radiation's
frequency. THE BIRTH OF PLANCK's CONSTANT
This meant that high frequency radiation could only be emitted or absorbed in events involving a single quantum of significantly high energy, explaining why high frequency events seemed unusually supressed by comparison to the classical physics.
3 The Photoelectric effect
3.1 Albert Einstein
126.96.36.199 In classical theory - Radiation absorbed by
a sheet of metal could release electrons if
the intensity or energy content of the beam
was sufficient to release the electron. In this
model the electron release would only be
related to the intensity, not the frequency
188.8.131.52.1 his experiment showed the opposite. Below
a certain frequency a beam may emit no
electrons however intense the beam is.
above that frequency a beam could emit
electrons however low the intensity
This puzzling behaviour became instantly understandable when you consider the beam of radiation as a stream of persisting quanta. An electron would be ejected if one of these quanta had collided with it and given up all its energy. The amount of energy in the quanta was directly proportional to the frequency, related by Planck's constant.
If the frequency were too low, then there would not be enough energy transmitted in the collision to enable the electrons escape.
The intensity of the beam, simply determined how many quanta were in the beam, and so how many electrons were involved in collisions and were able to escape. Increasing the intensity could alter the amount of energy in a single collision.
184.108.40.206.1.1 These Quanta became 'photons'
4 1925 + 1926
4.1.1 Matrix Mechanics
4.2 Erwin Schrodinger
4.2.1 Wave Mechanics
5 The Nuclear Atom
220.127.116.11 How come Alpha
particles were deflected
by a thin gold film
It was as astonishing as if a 15" naval round had recoiled on striking a sheet of toilet paper.
18.104.22.168.1 J.J Thompson's Plum Pudding model
(1897) of Atom's could make no sense
22.214.171.124.1.1 The Positive charge of the Gold Atoms, could not be
spread out as suggested, but must be concentrated at
the centre of the atom in order to provie enough
repulsion to deflect an alpha particle.
126.96.36.199.1.1.1 this gave way to the Solar System theory
188.8.131.52.184.108.40.206 Which led to yet more crisis - If electrons are constantly encircling an
atomic nucleus they are constantly changing direction. For this to work
they would have to radiate away some of their energy and gradually
decline to the centre of the nucleus. Atoms would be unstable and this
process of decay the spectra should no longer be as defined as the
spectra that balmer had uncovered
6 The Bohr Atom
6.1 Niels Bohr
220.127.116.11 Bohr took on some of the principle
thinking that Plank had used.
Rather than to suppose that
radiation could ooze in and out on
a sliding scale he assumed a system
that was rather more discrete.
Electrons he proclaimed could only
exist at certain permitted orbits.
(against the position a classical
physicist may take)
18.104.22.168.1 Using Planck's constant he proposed how
these radii could be determined. The
immediate consequence was that his theory
provided a more fitting model of an atom
THAT WAS STABLE. His mathematical
formula also led to the Balmer formula
discovered almost 30 years previously
once an electron was in an orbit, corresponding to the lowest permitted radius - it had nowhere else to go so no more energy could be lost. It may have got to this point by emitting energy as it dropped from higher orbits. This energy would be emitted as a single photon.
7 Compton Scattering
7.1 Arthur Compton
22.214.171.124 He found that scattered x-rays had
their frequency changed by matter.
with a wave model this could not
in the classical theory, it would be argued that the scattering process would be due to electrons in the atoms absorbing and re-emitting energy from the incident waves without altering the frequency
126.96.36.199.1 According to Planck's theory a change in
energy is equal to a change in frequency
which fitted, and thus Compton was able to
give a quantitive explanation for his findings
providing the most persuasive evidence to
date of the particle like character of
188.8.131.52.1.1 These Theories could
be ignored no longer