The Electromagnetic Spectrum

The Electromagnetic Spectrum

1. Radio

   • Radio waves is low energy waves that are used to communicate over long distances through radio and television. They are produced through vibrating electrons in a transmitting aerial. They can travel long distances. They make electrons in the antenna of your television or radio vibrate, and this is converted into the sound or images you see and hear when tuning in. They are used for communication because they bend around the Earth’s surface when transmitted.

2. Microwave

   • The microwaves are absorbed by the food molecules, causing them to vibrate and heat up, but because the heating occurs inside the food without warming the air, the food can cook unevenly. Glass, paper and many plastics do not absorb microwaves, metal reflects microwaves.

3. Infrared

   • Infrared waves are just below visible red light in the electromagnetic spectrum. ("Infra" means "below"), hence invisible to the human eye. They are emitted by all objects and sensed as heat. The amount of infra red radiation emitted by an object increases as its temperature decreases. They are used for many tasks, for example, remote controls for TVs and video recorders. Every object gives off infra red waves, we can use them to "see in the dark".

4. Visible

   • Visible light consists of different colours. Although it represents only a small part of the electromagnetic spectrum, it is the only band visible to the human eyes. It is essential for life on Earth, for example the process of photosynthesis in green plants cannot take place without visible light.

5. Ultra violet

   • Ultraviolet (UV) light is radiation with a higher frequency than violet light (ultra means beyond). It is invisible to the human eye. Sunlight contains UV light in addition to infrared and visible light. It is needed by humans to help the body produce vitamin D. Too much exposure to UV light can cause sunburn and skin cancers such as melanoma.

6. X-ray

   • X-rays are very high frequency waves, and carry a lot of energy. They will pass through most substances (including human flesh), and this makes them useful in medicine and industry to see inside things. It has such high energy that it can damage cells and tissues, and the genetic material inside cells. X-rays are produced when fast moving electrons give up their energy quickly. In an X-ray machine, this happens when electrons strike a metal terget made of tungsten.

7. Gamma ray

   • Gamma rays have a wavelength of about one- hundred- billionth of a metre. They have even more energy than X-rays and can cause serious damage to living cells. They can be used to kill cancer cells, used in medical diagnosis and find weaknesses in metals. They are produced when energy is lost from the nucleus of an atom. This could be due to the radioactive decay of nulcei or as a result of nuclear reactions.