The electromagnetic spectrum

Looking at the sun, it's easy to think that all it's sending out is heat and visible light. But there are other forms of energy radiating from the sun, which we can't see or feel. Just like the heat and the visible light, this energy also comes in the form of waves. The waves have both electric and magnetic properties. They are called electromagnetic waves.

Just like sound waves the electromagnetic waves have both frequency and wavelength. But unlike sound waves, which are made up of compressions and rarefactions of a medium, electromagnetic waves can travel through empty space. If that wasn't the case, they wouldn't be able to travel all the way from the sun, through empty space, to Earth. Some of the waves have a really long wavelength and a low frequency. While others have a very short wavelength and a high frequency.

When we look at all these different types of waves together, we are looking at something called the electromagnetic spectrum. Each part of the spectrum has different properties. On the long end of the spectrum we find radio waves. Their wavelength ranges from smaller than a football to larger than Earth. Radio waves carry signals across long distances so we can tune into radio stations or communicate on devices like walkie talkies.

Next on the spectrum are waves that have a shorter wavelength and a higher frequency -- microwaves. Microwaves carry more energy; enough energy to cook your food or provide signal for your cellphone. With shorter wavelength than microwaves and also carrying more energy are infrared waves, which are felt as heat. Infrared is used by doctors to treat sports injuries and by you: to change the channel with your TV remote. With the naked eye, we can't see any waves on this part of the spectrum.

So what waves can we see? Only this small part. This is called visible light. It's made up of many waves, each vibrating at a different frequency. Our brain interprets the different frequencies as different colours.

Together, the colours make up what we call the visible light spectrum. What we see as white light is actually a combination of all the colours in this spectrum. This is the only part of the electromagnetic spectrum that is visible to the naked eye. Beside visible light we find ultraviolet light. It has a higher frequency and shorter wavelength than visible light.

Ultraviolet rays stimulate our skin cells to produce vitamin D, which our bodies need. But too much exposure causes sunburn and sometimes even cancer. X-rays have even shorter wavelength than ultraviolet rays. X-rays have such a high frequency that they pass right through soft tissue, like our skin. Sending x-rays through a patient's body allows doctors to see what's going on inside.

Finally, on the end of the electromagnetic spectrum are gamma rays, which have the smallest wavelength and the highest frequency. They carry enough energy to kill livings cells, which is why gamma rays are sometimes used to kill cancer cells as well as sterilize food and medical equipment. So the next time you look up at the sun, remember that you are only seeing the visible light of the electromagnetic spectrum. There are so many other waves coming right at you.