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When and how were the waves discovered? By whom?
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The uses and applications of those waves
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Any scientific discoveries/proofs or research made possible by those waves
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Dispel any myths or misbeliefs about the waves
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Discuss how reflection, refraction and diffraction of the waves are utilized in
scientific fields, technology and/or in everyday life
Radio Waves, Microwaves, Infrared Rays, Ultraviolet Rays, X-Rays, and Gamma
Rays
Radio waves
1.
Radio waves were first predicted by mathematical work done in 1867 by Scottish
mathematical physicist James Clerk Maxwell. Maxwell noticed wavelike properties of light
and similarities in electrical and magnetic observations.
2.
Maxwell proposed equations that described light waves and radio waves as waves
of electromagnetism that travel in space, radiated by a charged particle as it undergoes
acceleration. In 1887, Heinrich Hertz demonstrated the reality of Maxwell's
electromagnetic waves by experimentally generating radio waves in his laboratory.
3.
Many inventions followed, making use of these 'Hertzian' waves to transfer
information through space. Radio telescopes look toward the heavens to view planets,
comets, giant clouds of gas and dust, stars, and galaxies. By studying the radio waves
originating from these sources, astronomers can lear
4.
n about their composition, structure, and motion. Radio astronomy has the
advantage that sunlight, clouds, and rain do not affect observations.
5.
An electromagnetic field (also called electromagnetic radiation) is a region in
space through which energy passes that has been created by electrically charged
particles. EMFs are produced by, radio waves (and others).
 Many people fear that EMFs cause cancer; however, a causal connection
between EMFs and cancer has not been established.
 Someone accused a phone manufacturer because they thought the radio waves
and electromagnetic fields emitted from their cell phone had given them brain
cancer.
 There are organized movements in several countries to enlighten the world about
the dangers of EMR (electromagnetic radiation). In the USA, there is The EMR
Policy Institute.
6.
Radio waves are reflected by charged particles in the upper atmosphere. This
means they can be sent and received over very long distances.
Microwaves
1.
Microwaves were first predicted by James Clerk Maxwell in 1864 by use of his
equations.
2.
During 1888 Heinrich Hertz proved the existence of microwaves by building a
device that produced and detected microwave radiation. His device used a horse trough, a
wrought iron point spark, Leyden jars, and a length of zinc gutter with a parabolic crosssection that worked as a reflection antenna. In 1894 J. C. Bose publicly demonstrated
radio control of a bell using millimeter wavelengths, and conducted research into the
broadcasting of microwaves.
3.
High-power microwave sources use specialized vacuum tubes to generate
microwaves. These devices operate on different principles from low-frequency vacuum
tubes, using the ballistic motion of electrons in a vacuum under the influence of controlling
electric or magnetic fields, and include the magnetron (used in microwave ovens); Radar
uses microwave radiation to detect the range, speed, and other characteristics of remote
objects. Development of radar was accelerated during World War II due to its great military
utility. Now radar is widely used for applications such as air traffic control, weather
forecasting, navigation of ships, and speed limit enforcement.
4.
Myths
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

Microwaves are non-ionizing radiation so according to many beliefs microwaves
cannot cause cancer, but can aid in it if exposed for too long.
It has not been shown conclusively that microwaves have significant adverse
biological effects at low levels. Some studies suggest that long-term exposure may
have a carcinogenic effect. This is separate from the risks associated with very
high-intensity exposure, which can cause heating and burns like any heat source,
and not a unique property of microwaves specifically.
During World War II, it was observed that individuals in the radiation path of radar
installations experienced clicks and buzzing sounds in response to microwave
radiation. This microwave auditory effect was thought to be caused by the
microwaves inducing an electric current in the hearing centers of the brain.
5.
Microwaves are reflected by metal surfaces; they pass through glass; they are
absorbed by water molecules; they are used to heat up food in microwave ovens.
Infrared Rays
1.
William Herschel, an amateur astronomer famous for the discovery of Uranus in
1781, made an important discovery in 1800. Herschel was familiar with Newton’s
discovery that sunlight could be separated into that separate chromatic components via
refraction through a glass prism. Herschel thought that the colors themselves might
contain different levels of heat, so he devised a clever experiment to investigate this.
Herschel passed sunlight through a glass prism to create a spectrum (the rainbow created
when light is divided into its color components) and measured the temperatures of the
different colors. He used three thermometers with blackened bulbs and placed one bulb in
each color while the other two were placed outside the spectrum as controls.
2.
Infrared is used in night vision equipment when there is insufficient visible light to
see. Infrared light sources can be used to augment the available ambient light for
conversion by night vision devices, increasing in-the-dark visibility without actually using a
visible light source.
3.
Weather satellites equipped with scanning radiometers produce thermal or infrared
images, which can then enable a trained analyst to determine cloud heights and types, to
calculate land and surface water temperatures, and to locate ocean surface features.
4.
Myths
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Infrared radiation is of longer wavelength than the visible light frequencies, and is
perceptible as heat. The main hazard to the eyes is that prolonged exposure (over
a matter of years) causes a gradual but irreversible opacity of the lens.
There is an immediate burning sensation in the skin surrounding the eyes should
they be exposed to arc heat. The natural human reaction is to move or cover up to
prevent the skin heating, which also reduces eye exposure.
Hyperpigmentation, scaling, and telangiectasia may occur from repeated IR
exposures of elevated temperatures, even if the skin is not burned.
Increased skin temperature can reduce DNA repair efficiency, and promote skin
cancer that is initiated by other agents.
5.
Diffracted infrared rays are used in remote controls for the television that we watch
every day.
Ultraviolet Rays
1.
UV radiation was discovered in 1801 when the German physicist Johann Wilhelm
Ritter observed that invisible rays just beyond the violet end of the visible spectrum
darkened silver chloride-soaked paper more quickly than violet light itself. He called them
"oxidizing rays" to emphasize chemical reactivity and to distinguish them from "heat rays",
discovered the previous year at the other end of the visible spectrum.
2.
Photography by reflected ultraviolet radiation is useful for medical, scientific, and
forensic investigations, in applications as wide spread as detecting bruising of skin,
alterations of documents, or restoration work on paintings. Photography of the
fluorescence produced by ultraviolet illumination uses visible wavelengths of light.
In ultraviolet astronomy, measurements are used to discern the chemical composition of
the interstellar medium, and the temperature and composition of stars. Because the ozone
layer blocks many UV frequencies from reaching telescopes on the surface of the Earth,
most UV observations are made from space.
3.
UV is widely used as a technique in chemistry to analyze chemical structure, the
most notable one being conjugated systems. UV radiation is often used to excite a given
sample where the fluorescent emission is measured with a spectrofluorometer. In
biological research, UV light is used for quantification of nucleic acids or proteins.
Ultraviolet lamps are also used in analyzing minerals and gems. In pollution control
applications, ultraviolet analyzers are used to detect emissions of nitrogen oxides, sulfur
compounds, mercury and ammonia, for example in the flue gas of fossil fired power
plants. Ultraviolet light can detect thin sheens of spilled oil on water.
4.
Overexposure to UVB radiation not only can cause sunburn but also some forms
of skin cancer. In humans, excessive exposure to all bands of UV radiation can result in
chronic harmful effects on the skin, eye, and immune system. All bands of UV radiation
damage collagen fibers and accelerate aging of the skin. Both UVA and UVB destroy
vitamin A in skin, which may cause further damage.
5.
In the solar tanning bed, the reflection of UV rays goes through the skin, tanning it.
X-Rays
1.
On 8 Nov, 1895, Wilhelm Conrad Röntgen (accidentally) discovered an image cast
from his cathode ray generator, projected far beyond the possible range of the cathode
rays (now known as an electron beam). Further investigation showed that the rays were
generated at the point of contact of the cathode ray beam on the interior of the vacuum
tube, that they were not deflected by magnetic fields, and they penetrated many kinds of
matter. A week after his discovery, Rontgen took an X-ray photograph of his wife's hand
which clearly revealed her wedding ring and her bones.
2.
X-rays are used to inspect canned goods and other packaged products. A
conveyor carries the goods past a beam of X-rays. If a container is improperly filled, or if it
contains a foreign substance, the X-rays set off an alarm or set into action a device that
removes the container from the conveyor. X-rays are similarly used to separate beryl from
granite and to inspect airplane and automobile parts, rubber goods, plastics, metal
castings, and a variety of other products.
3.
A radiograph is an X-ray image obtained by placing a part of the patient in front of
an X-ray detector and then illuminating it with a short X-ray pulse. Bones contain
much calcium, which due to its relatively high atomic number absorbs x-rays efficiently.
This reduces the amount of X-rays reaching the detector in the shadow of the bones,
making them clearly visible on the radiograph. The lungs and trapped gas also show up
clearly because of lower absorption compared to tissue, while differences between tissue
types are harder to see.
4.
Being exposed to X-rays carries a theoretical risk of triggering cancer at a later
date, as does exposure to background radiation. However, this risk is very low.
5.
Scattering of X-rays by the atoms of a crystal that produces an interference effect
so that the diffraction pattern gives information on the structure of the crystal or the identity
of a crystalline substance.
Gamma Rays
1.
The term gamma ray was coined by British physicist Ernest Rutherford in 1903
following early studies of the emissions of radioactive nuclei. The first gamma ray source
to be discovered historically was the radioactive decay process called gamma decay. In
this type of decay, an excited nucleus emits a gamma ray almost immediately upon
formation. Paul Villard, a French chemist and physicist, discovered gamma radiation in
1900, while studying radiation emitted from radium. Villard knew that his described
radiation was more powerful than previously described types of rays from radium, which
included beta rays, first noted as "radioactivity" by Henri Becquerel in 1896, and alpha
rays, discovered as a less penetrating form of radiation by Rutherford, in 1899.
2.
Gamma rays are used in industries to kill the harmful bacteria. Food irradiation is a
technology for controlling spoilage and eliminating food-borne pathogens, such as
salmonella. The result is similar to conventional pasteurization and is often called "cold
pasteurization" or "irradiation pasteurization." Like pasteurization, irradiation kills bacteria
and other pathogens that could otherwise result in spoilage or food poisoning.
3.
Radiation therapy kills cancer cells by damaging their DNA. Radiation therapy can
either damage DNA directly or create charged particles within the cells that can damage
the DNA. Cancer cells whose DNA is damaged beyond repair stop dividing or die. When
the damaged cells die, they are broken down and eliminated by the body’s natural
processes.
4.
Gamma rays cause damage at a cellular level and are penetrating, causing diffuse
damage throughout the body. Low levels of gamma rays cause a stochastic health risk,
which for radiation dose assessment is defined as the probability of cancer induction and
genetic damage.
5.