UV waves


external image Sunbathing.jpg

What are they?

Ultraviolet (UV) light has shorter wavelengths than visible light. Although UV
waves are invisible to the human eye, some insects, such as bumblebees,
can see them. This is similar to how a dog can hear the sound of a whistle
just outside the hearing range of humans.

Are they dangerous?

The harmful effects from exposure to ultraviolet (UV) radiation can be
classified as acute or chronic. The acute effects of UV-A and UV-B exposure are
both short-lived and reversible. These effects include mainly sunburn (or
erythema) and tanning (or pigment darkening). The chronic effects of UV exposure
can be much more serious, even life threatening, and include premature aging of
the skin, suppression of the immune system, damage to the eyes, and skin cancer

Where do they come from?

As with most forms of electromagnetic radiation, the principal sources of ultraviolet external image sky-dots-stars-night.jpg
waves are the stars,including the sun. Most of the ultraviolet radiation that strikes the
earth's atmosphere originates in the sun.The action of ultraviolet waves on oxygen in
the atmosphere creates a layer of ozone some 9 to 19 miles (15 to 30 km) above sea level.

How do we detect them?

This activity is a simple method for demonstrating UV light presence. When a
photon of UV energy is absorbed, it is reemitted by the quinine in tonic water
as a photon of visible light. This process is called fluorescence. The extent of
fluorescence that occurs is related to the amount of UV light resulting from the
angle of the sun (time of day and season of year).

What can they be used for?

1. In Medicine, Ultraviolet waves are effective in killing bacteria and viruses. Hospitals
use germicidal lampsthat produce these waves to sterilize equipment, water and air in operating rooms.
It is also used to treat acne and psoriasis.external image org_images_electromagnetic-spectrum.jpg
2. In Industry, the Food and Drug industry uses germicidal lamps to disinfect various types of products and
their containers. The main use of ultraviolet is in the manufacturing integrated circuits.
3. In Science, Scientists learn about the make up and energy levels of atoms by studying UV rays. Experts also
learn abut distant stars and galaxies by analyzing the UV rays that are given off. Artificial sources of ultraviolet light
are often used to stimulate the effects of solar ultraviolet radiation in the study of the deterioration of materials
on exposure to sunlight.
4. In Consumer Goods, Ultraviolet waves are used to identify materials by the glow or fluorescence under them. They are used to
make black lights. May food and drug companies use germicidal lamps to disinfect various types of products, and their containers.



In the table below, fill the cells with very brief notes. Use the other pages to gather the information from, and you may want to go outside of this wiki if you really can't find the information here (though I'd be surprised!).



Gamma
X-rays
UV
visible
IR
microwaves
radio
How are they generated?

They are generated by radioactive

atoms and in nuclear explosions.

They also come from

stars, black holes and pulsars.

X-rays are generated by an X-ray tube, a
vacuum tube that uses a high voltage to
accelerate the electrons released by a hot cathode
to a high speed.
They can come from the sun, but
you can get man made lamps for experimental
perposes, tanning ect... they produce
ultra violet rays, just as the sun does.

William Herschel conducted an
experiment measuring the difference
in temperature between the colours in the
visible spectrum. He placed thermometers
within each color of the visible spectrum.
The results showed an increase in temperature
from blue to red. When he noticed an even
warmer temperature measurement just beyond
the red end of the visible spectrum, Herschel had discovered infrared light!
Microwaves are essentially high
frequency radio waves, which are
made by different types of transmitter.
For example, in a phone, they are
generated by a transmitter chip and an antenna, while in a microwave oven they are generated by a 'magnetron'.
Radio waves are energy waves that are generated by a transmitter. Radio waves are also known as electromagnetic radiation and the typical shape of the wave produced by a transmitter is that of a sine wave.
How are they detected?

We detect gamma rays by using

telescopes, but they don't look like

normal telescopes.They observe gamma

rays indirectly, by monitoring flashes

of visible light. Gamma rays

are a form of radiation.

In hospitals the pictures were captured using
image receptors such as thin films and photographic plates
Now they use computer technology to generate the
images produced by X-Rays.
This activity is a simple method for demonstrating UV light presence. When a
photon of UV energy is absorbed, it is reemitted by the quinine in tonic water
as a photon of visible light. This process is called fluorescence. The extent of
fluorescence that occurs is related to the amount of UV light resulting from the
angle of the sun (time of day and season of year).

Our eyes cannot see infrared waves but
instruments that can sense infrared
energy — such as night-vision goggles
or infrared cameras–allow us to "see"
the infrared waves emitting from warm objects such as humans and animals.
Devices called Geiger Tube
Antennas designed to detect radio
waves are usually similar in size to the wavelength they want to detect.
This is why many radio antennas
have to be very long. If the
antennas are not close to the
size of the wavelength they do not usually do a good job of detecting the waves.
How might they be dangerous?
They are extremely harmful to living creatures,
which is why they're used to destroy cancerous cells
X- rays can damage cells and cause cause cell mutation which
can cause cancer or cell death. It can cause these illnesses as it
produces radiation as do lots of high frequency waves
The harmful effects from exposure to ultraviolet (UV) radiation can be
classified as acute or chronic. The acute effects of UV-A and UV-B exposure are
both short-lived and reversible. These effects include mainly sunburn (or
erythema) and tanning (or pigment darkening). The chronic effects of UV exposure
can be much more serious, even life threatening, and include premature aging of
the skin, suppression of the immune system, damage to the eyes, and skin cancer

Infrared waves are heat waves. If the cells
absorb too much infrared radiation the heating will damage or kill the cells.
Infrared from the sun causes sunburn.
If you use them regularly,
the fact that they are artificial,
there has been growing concern
that these waves can pose a
significant health threat.
Prolonged exposure to microwaves
is known to cause "cataracts" in your
eyes, which is a clouding of the lens,
preventing you from seeing clearly (if at all!) So don't make a habit of pressing your face against the microwave oven door to see if your food's ready!
Radio waves are not dangerous because they have a low frequency. Large doses of radio waves are believed to cause cancer, leukaemia and other disorders. Some people claim that the very low frequency field from overhead power cables near their homes has affected their health.
What are the main or most significant uses?
They can kill living cells, they can even kill cancerous cells.
X- rays can be used to look at the internal structure of objects, theyare often used in airport scanners as they can travel through fairly
thick objects without being scattered or absorbed
In Medicine, Ultraviolet waves are effective in killing bacteria and viruses. Hospitals use germicidal lampsthat produce these waves to sterilize equipment, water and air in operating rooms.
It is also used to treat acne and psoriasis.

-Night vision goggles pick up the infrared light emitted by our skin and objects with heat.-A remote control uses light waves just beyond the visible spectrum of light—to change channels on your TV.
-Infrared is also used for cooking in grills and toasters
The can be used for Microwave
ovens to cook food, they are used
in mobile phones to send and
recieve waves and satelite communication.
They can be used for transmitting sound and television signals, radio is used for the transmission of data in coded form. In the form of radar it is used also for sending out signals and picking up their reflections from objects in their path

Good work. A very good section on UV - well presented and good material. The table is comprehensive, though rather full - you need to be able to remember the key points!
B+

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