The first one hundred years of the photon:
No other sub-atomic particle holds such fascination for the physicist as the photon. More is probably known about the photon than about any other sub-atomic particle . Yet in spite of this the photon remains as shrouded in mystery as on the day its existence was first suspected by Einstein , almost a 100 years ago , in 1905 , when he discovered the cause of the photo-electric effect.
The properties of the photon have been observed extensively over many years , yet no explanations have been offered for any of these properties , it remains as elusive as ever. This is not surprising when one examines in detail exactly what these properties are :-
1. The photon has the amazing ability to retain it’s energy or identity intact over amazing distances. To understand what this means it must be understood that scientists are able to view objects that are billions of light years away , note that the operative word here is ‘light years ‘ and not kilometers or miles. Yet over these almost unimaginable distances the photon retains its identity , red light is still red , blue light is still blue etc., Ordinary waves such as sound waves or waves in water , tend to dissipate their energy with distance. If this had happened to the photon we would not be able to know anything of the Universe. It is this distinctive feature of the photon which enables us to gain so much information about the Universe we inhabit. A photon is either absorbed or retains its energy.
2. The energy of the photon varies inversely according to wavelength and frequency. This means that photons with longer wave lengths will have lower frequencies and less energy than photons with shorter wave lengths and higher frequencies , as demonstrated by the relation: f=c / l.
3.
Photons travel in straight lines , which is peculiar because
the photon also has the properties of a wave and waves tend to curve around
objects. Since earliest times it has been known that light (photons) travel in
straight lines because of the sharp shadows thrown by the sun.
4.
A photon is the ultimate manifestation of the property known
as wave-particle duality , that is the photon exhibits the properties of both a
wave and a particle depending upon how it is viewed. It possesses all the
properties of a wave such as diffraction , interference , reflection and
refraction and all the properties of a particle as for instance having a
definite energy , possessing momentum ,traveling in straight lines and the
property of being indivisible , it is
not possible to have half a photon.
5.
A photon has no mass . In spite of being categorized as a
particle a photon possesses no rest mass.
6.
A photon always travels with the speed of light (in a vacuum
) or 300,000 Km/sec. Nothing in the Universe can travel faster.
7. All electromagnetic radiation from radio waves to gamma waves are formed of photons . It is a mistake to think that only visible light is made up of photons.
With so many properties of the photon available for study , one would have thought that it should have been possible for some kind of a model to be constructed of the photon which would incorporate all these properties. This has never been done . While the mass and relative sizes of even pions and muons , which are secondary sub-atomic particles in the atomic nucleus , have been determined , no such attempts have been made with regard to the photon. The question has to be asked , is this a deliberate strategy ? The answer is an emphatic yes! It turns out that the concept of wave particle duality is central to the very existence of atoms , without the concept of wave-particle duality we would have had no explanation as to how or why atoms can exist , according to classical physics atoms cannot or should not exist. The importance of wave particle duality was paramount in quantum mechanics for the first thirty years , yet when in 1955 Lamb and Retherford discovered physical evidence for the emission and absorption of “virtual” photons by the electrons of the atom thereby offering a more viable and consistent alternative , the concept of wave particle duality ought to have been demoted in importance. Unfortunately it was so deeply entrenched in the physics of the time that it had taken on the status of a sacred principle and the question of phasing out of wave-particle duality could not even be considered. Hence the reticence on the part of physicists to try to evolve a structure for the photon.
In order to trace the reason for this reticence it is necessary to go back in time to the early twentieth century when the secrets of the atom were first being unlocked. It was soon apparent that the laws of classical physics which had worked so well in describing and defining the macro world , failed completely when applied to the sub-atomic world.
For instance classical
physics predicted that electrons orbiting the nucleus of the atom
would lose their energy through radiation and spiral in towards the nucleus.
This is a notable example of the
complete failure of classical physics when applied to the sub-atomic world. By
making use of obvious conclusions drawn
from the principles of classical physics
, namely the instability of any stationary structure of
charged particles and the emission of
radiation by a particle moving with acceleration , it is concluded that
atoms cannot exist ! This
illustrates the most impressive
contradiction derived from the difference between the predictions of classical
physics and experiment : Mathematical explanation of how according
to Classical physics the electron should spiral into the Nucleus:
A positively charged nucleus “holds” a negatively charged electron by the force of the Coulomb attraction. (It should be noted here that Rutherford’s experiments on the scattering of a particles by nuclei constitute direct experimental proof of the validity of Coulomb’s law at atomic distances.):
(1)
e
is the electron’s and protons charge (for the sake of
simplicity , we consider the most primitive atom , that of hydrogen ) a
is the atomic radius. For the atom to be stable , the force of attraction is
insufficient . This force must be balanced out by the corresponding force of
repulsion. This role is played by the centrifugal force :
(2)
Here m is the electrons
mass and v is its velocity. The equilibrium of forces in the electron’s
center-of-mass frame of reference makes it possible to find the velocity of the
electron in its orbit :
(3)
With the numerical values of
charge , the electron’s mass , and the radius of the “average “ atom this
yields 10 8 cm/s . This is almost three hundred times less than the
velocity of light , so we can ignore relativistic effects. Two more formulas
are needed . The first gives the total energy of the electron in the field of
the nucleus:
(4)
The second formula is that for
radiation intensity by a charge e moving with acceleration , in this case w
= v2a. :
(5)
If the electron emits I ergs each second , then it will over the time
interval
(6)
lose all its energy and spiral
into the nucleus. t is the classical electron lifetime in the orbit , it
is fantastically short : t = 10 –10s. Which means that atoms cannot
exist according to the laws of classical physics !
It was in order to resolve these differences between
the observed facts and their incompatibility with the theories of classical
physics that quantum physics came into existence.
The central core of principles governing quantum mechanics
is highly rigid and regulated . In this
respect it might be thought of as resembling
one of the modern dances ,
possessing stringent rules and protocol
, which are rigorously enforced and observed , yet outside these rules open to astonishing variations in
interpretation , and innovation.
Much the same could be
said of quantum mechanics with its core of
intricate mathematical theorems woven around certain inviolable
principles . Yet , apart from this open to practically any suggestion. To illustrate this unrivalled openness to new
ideas that quantum mechanics brought to the study of science ,
Neils Bohr coined the expression “Crazy theory “ meaning a theory
that was just crazy enough to be true. Such an approach was necessary , the
conventional ideas then in existence were deeply rooted and were bound in
formalism , a complete break from this tradition was needed if progress was to
be made. New ideas were not slow in
coming , already Einstein’s path breaking theory of Special relativity and General relativity had turned the scientific
world on its head , more was soon to follow . Werner Heisenberg , a one time
student of Neils Bohr , proposed his Uncertainty relation which states that “ A sub-atomic particle cannot have simultaneously a definite
co-ordinate and a definite momentum. “
Mathematically stated this is as follows , where p stands for momentum and x for position : 
This goes
completely against Newtonian physics which state that the speed and position of
every object can be measured at any
point in time. The wave-particle
duality of matter proposed by de Broglie and derived by him from Einstein’s
equation for the equivalency of energy and matter E = mc2
, was another such new theory.
Although strictly speaking de Broglie waves resemble a mathematical construction rather than classical waves as they
are normally thought of. The remarkable aspect of these ideas is that they are
seen to be moving away from the physically observed domain where empirical evidence is the main criteria , into the realm of philosophical thought based on theoretical precepts. For instance Werner
Heisenberg’s Uncertainty principle bears an uncanny similarity to Immanuel Kant’s philosophy. According to
Kant the scientist can never be completely “aware” of an external physical world : such a
world exists but in the act of perceiving or discovering it , we inevitably
colour and process it. While the wave-particle duality bears some resemblance
to Bishop Berkely’s philosophy , one aspect of which states that when for example no-one is present in a room ,
the room and its contents are in fact non-existent. The fundamental difference
between science and philosophy seems to lie
mainly in the fact that while the former is supported by mathematical
logic the latter is not.
The Double Slit Experiment:
There had long been a fierce difference of opinion between the supporters of Hugyens and Newton on whether light was a particle or a wave. While supporters of Christian Hugyens believed in the wave theory of light , Newton’s supporters believed that light was a shower of particles. In 1803 Thomas Young a young Englishman performed what he thought was the ultimate experiment to prove once and for all the wave nature of light. He set up an experiment as shown in Diagram 1. consisting of a light source , an intermediate screen with two slits which could be covered or uncovered at will and a screen on which the image from the light source was received. With only one slit open the result was as seen in Diagram 1.
Diagram 1.
As can be clearly seen the light passing through the screen results in a spot of light being formed on the image screen when only one of the slits are open. The next stage of the experiment is where Thomas Young made history . When both the slits on the intermediate screen are open , what we would expect to see on the image screen is something like Diagram 2.
Diagram 2
What we would expect to see on the screen is something like Diagram 2 , namely we would expect to see an intensification and enlargement of the blob of light seen on the image screen in Diagram 1. In fact what we actually see is illustrated by Diagram 3.
Diagram 3
What we see in Diagram 3 is that the result of light from the source going through the intermediate screen when both the slits are open is a pattern of light and dark bands on the image screen. This is the result of a phenomenon called interference. Only waves can experience interference. So it seemed that Thomas Young had conducted the ultimate experiment to prove that light was a wave. And so it remained for the next hundred years or so.
Eventually there came a time when technology had improved enough to allow the double slit experiment to be conducted with a very weak light source amounting to single photons being released one at a time . The results were stunning. Because it was found that even when single photon were released they followed the same pattern. A blob of light when only one of the slits was open and an interference pattern when both of the slits were open. ( Obtained over a period of time.) The point of interest here is that when both the slits were open a single photon would never occupy a place that had been a dark band in the original experiment. What did this mean ? Did the photon intuitively know when both the slits were open , was there some kind of super-luminal communication which allowed the photon to sense when the other slit was open ? This wasn’t the end of the experiment , it was tried with electrons , protons and neutrons , always with the same result.
The results of this experiment led Quantum physicists to believe that the photon possessed wave-particle duality i.e that it was both a wave and a particle at the same time.
“Aumic “
Theory states that the deviation of the sub-atomic particle is due to the “virtual
photon field”. When both slits are open the electron or neutron naturally
travels along the lines where the field
is most intense (i.e ., where the fields entering from slit A and B impinge ) ,
therefore the pattern found on the detecting screen is an interference pattern.
The
wave particle duality of matter :
The introduction of
discreteness and the indisputable proof of the quantum nature of light and
energy to the physical picture of the world had led to incomprehensible
and controversial quantum “jumps” which
if accepted at face value seemed to have no logical explanation . The idea of
duality , which asserts the specific nature of
micro-particles , eliminated the
need for quantum “jumps” by suggesting a “manipulation” between the particle and wave concepts while at the same time making irrelevant the
issue posed by classical physics of the loss of energy of the orbiting electron
, since by this model the electron was no longer localised. The uncertainty principle and the theory of the wave-particle duality of
matter, when taken together
seemed to offer a solution to the underlying question of how and why atoms
could exist.
It was largely due to
these criteria that the wave-particle
duality of matter , in concert with the idea of discreteness became one
of the corner stones of quantum mechanics and an inviolable principle . While
on the one hand , the discreteness of
light and energy had been proven by physical experiments conducted in the
classical style , on the other , the wave particle duality of matter was
supported by theory and
mathematical logic . Wave-particle duality is considered to exist not only for sub atomic particles
, but for all matter , the photon being a particle with no mass is regarded as being the ultimate expression of
wave-particle duality. The contradiction underlying the existence of mutually exclusive wave-like and particle like behaviour in a single entity , is one of the hall marks of quantum
physics.
Wave-particle
duality no longer a fundamental
requirement :
It is ironic that
with the advances made in our understanding of the structure and
working of the atom , wave-particle
duality is no longer needed , at such a basic level , to explain how electrons
can orbit within the atom without losing their energy and going into a spiral
towards the nucleus , or of how quantum
jumps by the electron are made possible . The person mainly responsible for this development was the American physicist , Richard
Feynman (among others ) , who suggested the possibility
of virtual interactions taking place
between electrons , a hypotheses which experiments , such as the Lamb shift ,seem to bear out . This
explanation was made possible by the
implementation of another aspect of the Heisenberg uncertainty relation . The
second uncertainty relation states that if an event takes place within a very
short space of time , one thousand trillionth
( 10 -15 )
of a second , or with a very low energy ,
the conservation laws are not
violated. Stated as 
where E stands for energy
and t stands for time. Thus
it was concluded that electrons in orbit around the nucleus constantly emit and
absorb “virtual “ photons . “Virtual” photons being
exactly the same as real photons with the distinction that the
interactions (emissions and absorptions ) are performed in such a short time
that they are to all purposes “virtual” transactions or interactions and do not therefore affect the Laws of
Conservation . These transactions enable electrons to maintain their stability.
Despite an alternative theory , in the form of the emission and absorption of “virtual” photons by electrons , becoming available to account for how electrons were able to orbit the atomic nucleus without being drawn into it , wave-particle duality was neither modified nor relegated to a place of lesser importance , it continued to maintain its place as an inviolable principle of quantum mechanics. This is more serious than it at first sounds. The intransigence of quantum mechanics in relation to this particular subject in effect rules out any speculation on a different model of the photon structure being formulated , based on its properties . Consider the implications of what this means , if the structure of the photon is in reality different from that postulated by the Quantum view , which is that a photon is simultaneously both a wave and a particle , it means that our perception of the physical world we live in is flawed. Further it would also mean that many of the opinions we have of physical phenomenon are similarly flawed. While wave particle duality does seem to offer a synthesis between matter and energy as implied by energy/matter equivalence it does so by distorting reality as we normally experience it. For instance in the “Double Slit Experiment “ , quantum mechanics claims that sub-atomic particles possessing a definite mass and weight , such as electrons , neutrons and protons , have the ability to split into two and pass through both the slits simultaneously , or that the sub-atomic particle is in some way “aware” that both the slits are open , which implies some kind of super luminal (faster than light ) communication taking place. This is obviously against our awareness of reality as we experience it at the macroscopic level. Our understanding of nature as observed through experiment is that matter/energy equivalence does exist but that it takes large amounts of power to effect such transformations which even our advanced technology is barely capable of providing. What it comes down to is this ; if the quantum model of the photon as simultaneously possessing the properties of both a particle and a wave is true , then it follows that matter/energy equivalence is an uncomplicated affair and that such transformations do occur quite spontaneously at the sub-atomic level. If on the other hand the quantum model of the photon is not true and it turns out that the photon is indeed what it seems to be from an observation of its behaviour and properties , namely the symbiosis of a particle and a wave , then obviously the quantum view of the world is flawed and some re-thinking has to be done. Notice the difference between these two definitions , quantum mechanics states that a photon ‘is’ a particle when viewed in one particular manner and equally that the photon ‘is’ a wave when viewed in another particular manner. There is no ambiguity in quantum mechanics on this subject , the photon according to this view is both a particle and a wave. The “Aumic” Theory as stated here affirms that the photon possesses the properties of both a wave and a particle , but that it does so , because of its physical structure , rather in the same manner that ultra-sound , which although a wave , behaves at times like a particle , as for instance when ultra sound is used in medicine to obliterate gall stones. Ultimately we have to decide which view point is ‘true’ and the only way in which it is possible to do this is to test our hypotheses against observation and experiment .The model of the photon structure as given in this thesis offers unequivocal answers to many of the seemingly unanswerable problems which beset present day science , such as the propagation of electromagnetic radiation , super conductivity , gravity and magnetism.
Quantum
mechanics:
The evolution of Quantum theory marked a milestone in the progressive history of physics , it opened new doors to knowledge and expanded the frontiers of human perception to the uttermost bounds and even beyond. The research and supporting mathematical documentation were meticulous , sometimes , as in the case of ascertaining Hideki Yukawa’s theory on the mediation of nucleons , extending over a period of several decades until supporting proof became available. In particular Quantum Mechanics played a great role in our understanding of the atom. Almost all of the discoveries made were the result of well planned experiments conducted in a logical and acceptable climate. Many of the incredible advances made in technology including the computers we use today , nuclear reactors , X-rays , the scanning tunnel microscope and the internet to name just a very few , are a direct result of advances made in Quantum mechanics . However in every epoch of human learning there have been always been some misconceptions on the nature of observed phenomenon , an inevitable consequence of the limited knowledge available at that particular time. It is not surprising that while the empirical based theories of quantum mechanics still hold good , many of the theory based perceptions are gradually unravelling . Quantum field theory might be one such instance. QFD based its own theory on the precepts put forward by Maxwell , which have proven to be false.