Microwaves are most commonly known for their use in microwave ovens, but they are also used for communications, satellites and many other things. The microwaves have quite short wavelengths, so they are easily absorbed by water. In a microwave oven, the waves are absorbed by the water in the food, and their energy is converted to heat energy. This helps to quickly and effectively cook the food. Exposure to highly concentrated microwaves can be dangerous as the same could happen to a human. This was a serious problem when microwave ovens were first used, although their design has now improved to prevent this happening. There is concern that the microwaves used in mobile phones could have a damaging effect on people brains, because of their concentration and short wavelength.
Next in the spectrum are infrared rays. They are not visible but can be detected using infrared film. Most people use infrared rays everyday on devices such as TV remote controls. These send an invisible infrared signal to control the TV. Exposure to concentrated infrared rays can cause burning, but this is uncommon.
Visible rays are the colours we can see – red, orange, yellow, blue, green, indigo and violet – ‘the colours of the rainbow.’ These seven colours are the only part of the spectrum that the human eye can see. These rays are used for photography and we use them everyday just to see things and identify colours.
Ultraviolet light, also known as UV light, is next on the spectrum. The human eye cannot see it but other animals can. For example, a human might look at a flower and see it as red, but a be may look at it and see it a totally different colour because the flower is actually reflecting ultraviolet light as well. Ultraviolet light can be dangerous because it can kill and mutate cells in the body. This is why you can get skin cancer from sunbathing without a sunscreen containing a UV filter – because the sun's rays contain UV light. This risk has been greatly increased in the last few years because the earth’s natural UV filter – the ozone layer – has holes in it caused by CFC’s. This allows far more harmful UV rays to reach our skin. However, the fact that UV rays kill human cells can be used to an advantage as they are used to treat cancer buy killing the cancerous cells in the body. This can be risky because it is vital not to kill the living ones.
X – Rays are used in hospitals because they are very high energy. They can pass through skin, muscle and body tissue, but are absorbed by the bone, because it has a lot of calcium in it. This enabled medical staff to look at the shape and outline of a patient’s bones, to check for breakage’s or abnormalities. Patients can also be given a Barium meal so they can see their gut. The barium absorbs the rays in a similar way to the calcium in the bones so the digested meal will show up when an X-ray of the patient’s intestine is taken.
The last type of wave in the electromagnetic spectrum is a gamma ray. These rays have even higher energy than X-rays do. They can even pass through metal, which means they can be use to check for hairline cracks in metal structures, for example aeroplane wings, where this would be very important. Like X-rays and UV rays, gamma rays can be used to kill cancerous cells in the body. However, very serious safety precautions must be taken when using these types of rays, as they can harm people very badly, and also cause cancer.
