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Did you know that not only light and heat come from the sun? Many other forms of energy from the sun also reach this planet. For example, another form of radiant energy that comes from the sun other then light is ultraviolet radiation. Ultraviolet radiation may be considered dangerous to humans, because it causes skin cancer. That is why it is recommended to wear sun screen on a hot day, because more ultraviolet radiation reaches the earth. So what is the electromagnetic spectrum? The electromagnetic spectrum is an arrangement of types of visible light and invisible radiant energy, like ultraviolet radiation. Radiation does not need matter to travel in, therefore light rays and other invisible radiant energy can travel through space. That is why the light and the ultraviolet rays from the sun can reach earth, even though there is a vast distance of space between the two.
Different colours of light have different wavelengths and frequencies. Red, the first colour in the solar spectrum, has a wavelength of 700 nanometres (nm), when it is in a vacuum. It also has a frequency of 4.3 X 10(to the power of 14) Hertz. Purple, the last colour, has a shorter wavelength, only about 400 nm in a vacuum. However, it has a higher frequency, 7.5 X 10(to the power of 14) Hertz. When different colours hit a transparent object, they all refract at a different angle depending how long their wavelengths are and how fast their frequency is. This explains why the colours that make up white light are separated as they pass through a prism. If all the colours had the same wavelength and frequency, they would refract at the same angle, therefore when the colours come out of the prism there would be no spectrum; instead, there would be a white beam of light, since all the colours merged together makes white light.
There are six types of radiant energy arranged in the electromagnetic spectrum, starting with the type of radiation that has the longest wavelength and ending at the radiation with the shortest wavelength. The order of the arrangement starts off with radio waves (the longest), infrared radiation, visible light, ultraviolet radiation, X rays, and then finally gamma rays (the shortest). Humans can only see visible light, however, in some animals, their eyes are able to detect radiation that would be invisible to us (like ultraviolet radiation). Visible light only makes up a small portion of the electromagnetic spectrum, the invisible waves make up the biggest portion. These type of radiation affect us in many different ways, because these type of waves all have different uses and purposes.
The solar spectrum.
The next page will explain these types of radiation on the next page
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