Microwaves Microwaves are a form of energy. Those with a frequency of 2.45 thousand million hertz can be absorbed by water molecules. This gives the molecules more energy and the water heats up. So any food containing water can be cooked by microwaves. This could also be dangerous as our bodies are mostly water. The waves are absorbed by metal so microwave ovens have metal sheets or mesh around the cooking area to protect people. Contact with microwaves of the right frequency could cause a ‘cold burn’. Mobile phones do not use the same frequency as microwave ovens. This is one reason the Health Protection Agency says they are safe to use.

Infra red radiation Infra red is also known as heat radiation. It is absorbed by soft tissue causing it to heat up. Too much infra red can cause burns. For example, too much sun exposure can cause sun burn.

Visible light Blue-violet light on the visible light spectrum can cause damage to retina cells, increasing the risk of developing age-related macular degeneration. Macular degeneration is one of the most common causes of vision loss in one or both eyes for people over the age of 50. A common first symptom of the disease is a blurry spot near the centre of vision. As the disease progresses further, the blurry spot may grow in size. Affected individuals may notice blank spots in their central vision or that objects appear to have lost some of their brightness.

Ultraviolet radiation UV - is found naturally in sunlight. We cannot see or feel ultraviolet radiation, but our skin responds to UV exposure by burning or turning darker over time (a sun tan). This happens as our bodies attempt to reduce the amount of ultraviolet radiation reaching deeper skin tissues. Darker skins absorb more ultraviolet light, so less ultraviolet radiation reaches the deeper tissues. This is important, because ultraviolet radiation can cause cells to become cancerous. We should wear UV blocking sunscreen on sunny days to avoid skin cancer. Overexposure of our eyes to ultraviolet radiation can cause blindness, so we should wear hats and sunglasses on sunny days.

X-rays Although x-rays mostly pass through the body, some parts can absorb the radiation. The cells in these areas may become damaged if they are exposed too much. Large doses can eventually cause cancerous changes and may kill cells. Children and babies are most at risk, so these scans are rarely used on pregnant mothers. Adults can recover from small doses (e.g. two x-rays a year), but the reproductive organs are covered where possible to prevent mutations (changes in DNA) in sperm and egg cells. Radiographers stand behind a screen to take the x-rays to reduce their exposure.

Gamma rays Gamma rays are dangerous. If their high energy is absorbed by a cell, it may cause cancerous changes in the cell or kill it.