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WAVE THEORY
Group 2:
Buensuceso, Elagio, Emman, Gines, Diokno
Contents
Huygens’ Wave Theory
Thomas Young’s Double Slit Experiment
EM Wave Thoery
Hertz’s Experiment on EM Waves
Huygens’ Wave Theory
Huygens’ Wave Theory
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In the late 1600s, many
people began asking if
light is made up of
particles, or waves ?
Sir Isaac Newton, a
famed scientist,
supported the theory
that light was made up
of tiny particles,
maintaining the stance
of previous scientists.
Light
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However, we know that light is part of
the electromagnetic spectrum, the spectrum is
the collection of all waves, which
include visible light, Microwaves, radio waves (
AM, FM, SW ), X-Rays, and Gamma Rays.
This was proven eventually in 1678, by a Dutch
Scientist named Christiaan Huygens.
Christiaan Huygen
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Christiaan Huygens,
believed that light was
made up of waves
vibrating up and down
perpendicular to the
direction of the light
travels (transverse
waves), and therefore
formulated a way of
visualizing wave
propagation.
This became known as
'Huygens' Principle'.
Huygens’ Wave Theory
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Huygens’ theory was
the successful theory
of light wave motion
in three dimensions.
It also suggested that
light wave peaks form
surfaces like the
layers of an onion.
Wave Theory
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In a vacuum, or other
mediums, the light waves
are spherical, and these
wave surfaces advance
or spread out as they
travel at the speed of
light.
This theory explains why
light shining through a pin
hole or slit will spread out
rather than going in a
straight line.
Newton vs Huygens
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Some of the experiments
conducted on light theory,
both the wave and particle,
had some unexplained
results: as Newton could
not explain the
phenomenon of light
interference, this forced
Newton's particle theory in
favor of the wave theory.
However, it was eventually
realized that matter and
waves exhibited properties
of the other.

This was due to the
unexplained
phenomenon of light
Polarization - scientists
were familiar with the
fact that wave motion
was parallel to the
direction of wave travel,
NOT perpendicular to
the to the direction of
wave travel, as light
does.
Huygens’ Principle
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He also found that a surface
containing many separate
wave sources appeared as
a single wave front with the
shape of the surface. This
wave front is termed a
'Huygens combination' of
the separate waves.
This explains how matter's
spherical
In-waves
are
formed. The Out-waves of
others combine to form a
Huygens 'combination wave
front' which forms the
spherical In-wave of our
wave-centers.

Christian Huygens proposed a hypothesis for the geometrical
construction of the position of a common wavefront at any instant
during the propagations of waves in a medium. The postulates are:

Every point on the given wavefront called primary wavefront* acts as a
fresh source of new disturbance, called secondary wavelets** that travel
in all directions with the velocity of light in the medium.

A surface touching these secondary wavelets tangentially in the forward
direction at any instant gives a new wavefront at that instant. This is the
secondary wave front.
* - The envelope of all wavelets in the same phase - having received light from sources in the
same phase at the same time is called a wave front.
** - All points lying on small curved surfaces, that receive light at the same time from the same
source (primary or secondary) are called wavelets.
Thomas Young’s Double
Slit Experiment
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The double-slit experiment in quantum mechanics is an experiment
that demonstrates the inseparability of the wave and particle natures
of light and other quantum particles. A coherent light source
illuminates a thin plate with two parallel slits cut in it, and the light
passing through the slits strikes a screen behind them. The wave
nature of light causes the light waves passing through both slits to
interfere, creating an interference pattern of bright and dark bands
on the screen. However, at the screen, the light is always found to
be absorbed as discrete particles, called photons.

If the light travels from the source to the screen as particles, then the
number that strikes any particular point on the screen should be
equal to the sum of those that go through the left slit and those that
go through the right slit. In other words, the brightness at any point
should be the sum of the brightness when the right slit is blocked
and the brightness when the left slit is blocked. However, it is found
that blocking one slit makes some points on the screen brighter and
other points darker. This can only be explained by the alternately
additive and subtractive interference of waves, not the exclusively
additive nature of particles.
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Although the double-slit experiment is now often referred to in the
context of quantum mechanics, it is generally thought to have been
first performed by the English scientist Thomas Young in the year
1801 in an attempt to resolve the question of whether light was
composed of particles (Newton's "corpuscular" theory), or rather
consisted of waves traveling through some ether, just as sound
waves travel in air. The interference patterns observed in the
experiment seemed to discredit the corpuscular theory, and the
wave theory of light remained well accepted until the early 20th
century, when evidence began to accumulate which seemed instead
to confirm the particle theory of light.
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It was shown experimentally in 1972 that in a Young slit system
where only one slit was open at any time, interference was
nonetheless observed provided the path difference was such that
the detected photon could have come from either slit. The
experimental conditions were such that the photon density in the
system was much less than unity.
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A Young double slit experiment was not performed with anything
other than light until 1961, when Claus Jönsson of the University of
Tubingen performed it with electrons, and not until 1974 in the form
of "one electron at a time", in a laboratory at the University of Milan,
by researchers led by Pier Giorgio Merli, of LAMEL-CNR Bologna.
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The results of the 1974 experiment were published and even made
into a short film, but did not receive wide attention. The experiment
was repeated in 1989 by Tonomura et al at Hitachi in Japan. Their
equipment was better, reflecting 15 years of advances in electronics
and a dedicated development effort by the Hitachi team. Their
methodology was more precise and elegant, and their results
agreed with the results of Merli's team. Although Tonomura asserted
that the Italian experiment had not detected electrons one at a
time—a key to demonstrating the wave-particle paradox—single
electron detection is clearly visible in the photos and film taken by
Merli and his group.
EM Wave Theory
Electromagnetic waves
It consists of electric and magnetic field components which oscillate in
phase perpendicular to each other and perpendicular to the direction
of energy propagation.
EM wave theory
The theory of electromagnetic waves was first postulated by James
Clerk Maxwell and was confirmed by Heinrich Hertz.
Maxwell derived a wave form of the electric and magnetic equations,
revealing the wave-like nature of electric and magnetic fields, and their
symmetry.
Maxwell proved that light therefore is an electromagnetic wave through
his equations.
EM wave theory
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A spatially-varying electric field generates a time-varying magnetic
field and vice versa. Neither can exist by themselves.
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Therefore, as an oscillating electric field generates an oscillating
magnetic field, the magnetic field in turn generates an oscillating
electric field, and so on.
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These oscillating fields together form an electromagnetic wave.
Electromagnetism
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Electromagnetic waves are a form of traveling electric and magnetic transverse
waves
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A charged (positive/negative) particle can create an electric field around it. The force
of an electric field acts to electric charges just like how a gravitational field would act
to masses.
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When the charge start to oscillate, back and forth, the oscillation of the electric field
will create a magnetic field that is at right angles to the electric field
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The oscillation of the magnetic field would create another electric field and continue to
create each other in the process. Unlike a STATIC field, a wave cannot exist unless it
is moving. Once created, an electromagnetic wave will continue on forever unless it is
absorbed by matter.
Hertz’s Experiment on EM
Waves
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In 1887, Hertz designed a brilliant set of experiments that tested
Maxwell's hypothesis. He used an oscillator made of polished brass
knobs, each connected to an induction coil and separated by a tiny
gap over which sparks could leap. Hertz reasoned that, if Maxwell's
predictions were correct, electromagnetic waves would be
transmitted during each series of sparks. To confirm this, Hertz
made a simple receiver of looped wire. At the ends of the loop were
small knobs separated by a tiny gap. The receiver was placed
several yards from the oscillator.
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According to theory, if electromagnetic waves were spreading from
the oscillator sparks, they would induce a current in the loop that
would send sparks across the gap. This occurred when Hertz turned
on the oscillator, producing the first transmission and reception of
electromagnetic waves. Hertz also noted that electrical conductors
reflect the waves and that they can be focused by concave
reflectors. He found that nonconductors allow most of the waves to
pass through. Another of his discoveries was the photoelectric
effect.
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Earlier in 1886, Hertz developed the Hertz antenna receiver. This is
a set of terminals that is not electrically grounded for its operation.
He also developed a transmitting type of dipole antenna, which was
a center-fed driven element for transmitting UHF radio waves. These
antennas are the simplest practical antennas from a theoretical point
of view.
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Hertz made observations of the photoelectric effect and of the
production and reception of electromagnetic (EM) waves using an
apparatus. His receiver consisted of a coil with a spark gap,
whereupon a spark would be seen upon detection of EM waves. He
placed it in a darkened box to see the spark better. He observed that
the maximum spark length was reduced when in the box. A glass
panel placed between the source of EM waves and the receiver
absorbed ultraviolet radiation that assisted the electrons in jumping
across the gap.
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When removed, the spark length would increase. He observed no
decrease in spark length when he substituted quartz for glass, as
quartz does not absorb UV radiation.
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Through experimentation, he proved that transverse free space
electromagnetic waves can travel over some distance. This had
been predicted by Maxwell and Faraday. With his apparatus
configuration, the electric and magnetic fields would radiate away
from the wires as transverse waves. Hertz had positioned the
oscillator about 12 meters from a zinc reflecting plate to produce
standing waves. Each wave was about 4 meters. Using the ring
detector, he recorded how the magnitude and wave's component
direction vary. Hertz measured Maxwell's waves and demonstrated
that the velocity of radio waves was equal to the velocity of light. The
electric field intensity and polarity was also measured by Hertz.
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His discoveries would later be more fully understood by others and
be part of the new "wireless age". In bulk, Hertz' experiments
explain reflection, refraction, polarization, interference, and velocity
of electric waves.
Sources
http://en.wikipedia.org/wiki/Waveparticle_duality#Huygens_and_Newton
http://www.nightlase.com.au/education/optics/light.htm
http://www.juliantrubin.com/bigten/youngdoubleslit.html
http://en.wikipedia.org/wiki/Electromagnetic_radiation
http://science.hq.nasa.gov/kids/images/ems/consider.html
http://physics.tamuk.edu/~suson/html/4323/emtheory.html
http://www.juliantrubin.com/bigten/hertzexperiment.html
http://en.wikipedia.org/wiki/Heinrich_Hertz#Electromagnetic_research
http://en.wikipedia.org/wiki/Heinrich_Hertz
http://people.seas.harvard.edu/~jones/cscie129/nu_lectures/lecture6/hertz/Hertz
_exp.html