05+DANGERS+AND+USES+OF+EM+WAVES

2.5 Demonstrate an understanding that the potential danger associated with an electromagnetic wave increase with increasing frequency.
2.6 Relate harmful effects, to life, of excessive exposure to the frequency of the electromagnetic radiation, including: c) ultraviolet: damage to surface cells and eyes, leading to skin cancer and eye condions. d) X-rays and gammay rays: mutation or damage to cells in the body

2.7 Describe some of the uses of electromagnetic radiation: a) radio waves: including broadcasting, communications and satellite transmissions b) mircowaves: including cooking, communications and satellite transmissions c) infrared: including cooking, thermal imaging, short range communications, optical fibres, remote controls and security systems d) visible light: including vision, photography and illumination e) ultraviolet: including security marking, fluorescent lamps, detecting forged bank notes and disinfecting water f) X-rays: including observing the internal structure of objects, airport security scanners and medical X-rays g) gamma rays: including sterilising food and medical equipment, and the detection of cancer and its treatment

__**Electromagnetic Waves**__ The higher the﻿ frequency, the more dangerous the waves are and they could damage you more easily.

**Radio Waves**: are low frequency waves with a long wavelength and are the biggest waves in the spectrum.
 * They are used to carry information and sound and video from radios and other such electronic items.
 * Radio waves are not harmful and they can be reflected off the ionosphere, sometimes they are refracted by buildings and mountains.
 * They are used to broadcast shows and they are used to communicate with people. [[image:http://www.bbc.co.uk/schools/gcsebitesize/science/images/18_radio_waves.gif width="519" height="288" align="left" caption="microwaves pass through the atmosphere, radio waves relected through a charged layer of the upper atmosphere, signal received even though transmitter and receiver are not in the line of sight "]]

**Microwaves**: have a slightly higher frequency than radio waves and they can pass through glass, paper, ceramic and plastic. They are smaller than radio waves.
 * These waves are absorbed by food and water. Unlike radio waves, they can damage you by internally heating your body cells. They can transmit signals like mobile phone calls.
 * Certain microwave radiation wavelengths pass through the Earth's atmosphere and can be used to transmit information to and from satellites.

**Infared**: Infared radiation is absorbed by the skin and we feel it as heat, but we cannot see it. It is used in heaters, toasters and grills. It is also used for television remote controls and in optical fibre communications. This wave is used to treat skin diseases and relieve the pain of sore muscles. Infared can cause us sunburn. They can be used in thermal imaging cameras which pick up heat, they can be used by police in helicopters so they can catch criminals in the dark.

**Visible Light**: They are the only waves we can see. When we see it it is white light but if you look at through a prism you can see the colour spectrum (the R A <span style="color: #ffff00; font-family: Arial,Helvetica,sans-serif; font-size: 110%;">I <span style="color: #00ff00; font-family: Arial,Helvetica,sans-serif; font-size: 110%;">N <span style="color: #008000; font-family: Arial,Helvetica,sans-serif; font-size: 110%;">B <span style="color: #0000ff; font-family: Arial,Helvetica,sans-serif; font-size: 110%;">O <span style="color: #800080; font-family: Arial,Helvetica,sans-serif; font-size: 110%;">W !!!). The light gets refracted in the prism so it shows all the colours.
 * <span style="color: #ff1f66; font-family: Arial,Helvetica,sans-serif; font-size: 110%;">Infrared is nearest to the red side of the spectrum and Ultraviolet is closest to the violet side of the spectrum. All the colours have different wave lengths and as red is closest to infrared, it has the longest wavelengths in the visible light spectrum, just as violet has the shortest.
 * <span style="color: #ff1f66; font-family: Arial,Helvetica,sans-serif; font-size: 110%;">The sun is our natural light source but we can get light from light bulbs. The colour we see when we look at something is that colour from the spectrum being reflected, all the o ﻿ ther colours are absorbed.

[[image:http://t1.gstatic.com/images?q=tbn:ANd9GcSPl_lazy9_eUhIpBFBTKYuiOTDnHS4BEC4ZUZpKaB2QhS5Knsd7w&t=1 width="225" height="225" align="right"]]
//<span style="font-family: Arial,Helvetica,sans-serif; font-size: 110%;">The wavelengths detectable by the human eye represent only about 3% of the total electromagnetic spectrum. // <span style="color: #800080; font-family: Arial,Helvetica,sans-serif; font-size: 110%;">** ﻿ ** Visible light is also used for pictures.

<span style="color: #800080; font-family: Arial,Helvetica,sans-serif; font-size: 110%;">**Ultraviolet Light**: Ultraviolet radiation is basically a form of energy travelling through space. UV light has shorter wavelengths than visible light. Though these waves are invisble to the human eye, some insects can see them.
 * <span style="color: #800080; font-family: Arial,Helvetica,sans-serif; font-size: 110%;">The Sun is a big source of ultraviolet rays. 99% of the Sun's rays are in the form of visible light, ultraviolet rays, and infared rays. Man-made lights also emit UV. UV rays can be divided into 3 different wavelengths: UV-A, UV-B and UV-C. This is a way of classifying the rays (based on the amount of energy they contain. UV-C is the most energetic and the most harmful, UV-A is the least energetic and the least harmful. UV-C doesn't reach the Earth's surface, because of the ozone layer.
 * <span style="color: #800080; font-family: Arial,Helvetica,sans-serif; font-size: 110%;">Ultraviolet light can damage the skin. However, the positive effect of UV exposure is the production of vitimin D in the skin. Uv light can also destroy bacteria.
 * <span style="color: #800080; font-family: Arial,Helvetica,sans-serif; font-size: 110%;">Sun beds are just U.V light, and whilst giving you a tan, they can also give you skin cancer so they are more dangerous than they seem.


 * <span style="color: #ff1f66; font-family: Arial,Helvetica,sans-serif; font-size: 110%;">X - rays: **<span style="color: #ff1f66; font-family: Arial,Helvetica,sans-serif; font-size: 110%;">X-rays have short wavelengths, but high energy. Although it is invisble to our eyes, x-rays can be seen on film.
 * <span style="color: #ff1f66; font-family: Arial,Helvetica,sans-serif; font-size: 110%;">The danger of X-rays is that it can cause skin burns if you are exposed for too long.
 * <span style="color: #ff1f66; font-family: Arial,Helvetica,sans-serif; font-size: 110%;">X-rays are able to pass through tissue, not bones. This factor about X-rays is extremely helpful in hospitals when doctors are looking at broken bones; X-rays are used to see bones, cancers and reveal heart problems.
 * <span style="color: #ff1f66; font-family: Arial,Helvetica,sans-serif; font-size: 110%;">X-rays were first observed in 1895 by Wilheim Conrad Roentgen, a German scientist who found them by accident when he was experimenting with vacuum tubes.
 * <span style="color: #ff1f66; font-family: Arial,Helvetica,sans-serif; font-size: 110%;">Radiation from medical procedures have caused 50% and over of cancererous cells in the body.

<span style="color: #800080; font-family: Arial,Helvetica,sans-serif; font-size: 110%;">**Gamma rays**: These rays have the smallest wavelengths and the most energy. Gamma rays travel to Earth across vast distances of the universe, only to be absorbed by our atmosphere.

> ==== ====
 * <span style="color: #800080; font-family: Arial,Helvetica,sans-serif; font-size: 110%;">These rays can be produced by supernova explosions, destructions of atoms, neutron stars and black holes.
 * <span style="color: #800080; font-family: Arial,Helvetica,sans-serif; font-size: 110%;">Gamma rays can kill living cells, which is why hospitals use it to their advantage to kill cancerous cells.
 * <span style="color: #800080; font-family: Arial,Helvetica,sans-serif; font-size: 110%;">Gamma ray bursts can release more energy in 10 seconds than the Sun will emit in its entire 10 billion-year-lifetime. So far, all of the bursts have come from outside the Milky Way Galaxy. Scientists think they will occur every few million years in the Milky Way.
 * ==== Gamma rays are used to sterelise medical equipment which obviously stops from spreading diseases and cells. ====