Radiation

What is radiation?

Movement of energy from one area to another is known as radiation. Xrays, the energy generated in nuclear power plants and the warmth we feel from the sun are all results of radiation. Radiation can be both useful and destructive.

Three forms of radiation

1. Electromagnetic (EM) radiation

This form of radiation is the least destructive of the three. Sometimes it is known as radiant or light energy. It gets this name as it is able to easily pass through air and just as easily through a vacuum. It is also often able to pass through solid materials such as glass. A common example of EM radiation is sunlight. It's energy is used in many ways by all forms of life Earth. In human life the sun is a part of many different cultures: the Incas in Central America, the Egyptians in Africa and the Greeks all worshiped the sun as a god, while other religions and cultures view it as a gift from their gods.

For many forms of life the sun is essential for sight as it reflects the light off objects to the eye. The sun's heat (infrared radiation) has created the many climates now known on Earth. A final use of the sun is Ultraviolet radiation which stimulates the skin's cells to produce vitamin D which is vital to humans.

EM radiation is arranged into the electromagnetic spectrum (the orderly classification of energy being used). Beginning with the highest energy (so the shortest wavelength) and moving down to the lowest energy (so the longest wavelength) the categories of the electromagnetic spectrum are gamma rays, X-rays, ultraviolet radiation, visible light, infrared radiation and radio waves.

Radio waves are the most commonly used as they are the least harmful. Radio waves are used to communicate (for example: transistor radios and walkie-talkies), to broadcast by satellite, to cook food in the microwave, and many other applications. X-rays are part of daily use for doctors and hospitals. The X-rays produced by the machine are absorbed into the body, passing through soft tissue and absorbed into the bone producing a picture in which one can see the bones. These X-rays are of a low intensity as high intensity X-rays can destroy tissue. These high intensity beams are used for the treatment of tumours as the cancerous cells are vulnerable to X-rays. Gamma rays produce the highest energy and most destructive rays. These gamma rays are emitted from the nuclei of atoms when they undergo radioactive decay. They have about the same energy as a very high intensity X-ray.

Detecting EM radiation is difficult, human beings are only able to feel and see a small amount of the electromagnetic spectrum. Telescopes and antennas are used to detect electromagnetic radiation. The EM radiation is then projected onto some kind of electronic detector.

2. Mechanical radiation

Mechanical radiation requires an a material to generate energy from one place to another. An example of mechanical radiation is sound because it is caused by vibration and, for example, cannot travel through a vacuum, but can travel through a liquid. Another example of this form of radiation is ultrasound which, to medicals, is very important. Ultrasounds work by the transmission of soundwaves through the body, these are used to check the fetus in a uterus or to detect abnormal growths.

Mechanical radiation is mainly produced by vibration so detectors for this form are usually objects that vibrate such as membranes in electrical equipment. Also devices which detect volcanic action, earthquakes or underground nuclear weapon tests are of great importance to science.

3. Particle radiation

This form of radiation occurs when radioactive materials (such as uranium) decompose causing particles to collide and produce energy. When this occurs, the particles physically move. Like EM radiation, particle radiation is also able to travel through a vacuum, however, the particles move less freely through a solid material because there are often many collisions, losing a great amount of energy. Each particle travels at its own speed and direction (usually outwards though) because each particle has its own size.

It is impossible to detect such radiation with the bear eye. Special detectors that absorb or catch these particles are used. After being caught the particles can then be observed.

Like EM radiation, particle radiation is used in a similar way in medicine in the detection of tumours and particle radiation is the main radiation that comes from nuclear power plants which generate electricity for many countries.

Information about radiation was found on Encarta Encyclopedia '96.

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