Visible white light is actually made up of a whole range of colours. It is the portion of the electromagnetic spectrum that is visible by the human eye. When is passes through a glass prism, the light is separated into 7 colours and this process is called dispersion. The colours are red, orange, yellow, green, blue, indigo and violet. The red colour, Infrared, has the longest wavelength, and the violet, UltraViolet, has the shortest wavelength. The sun is a natural source of visible light.
The uses of Light: Light allows us to see objects. Different objects absorb certain light and reflect away the other colours. Thus different objects have different colours. The colour of the objects is determined by what light is absorbed and what light is reflected back to our eyes.
Dangers : Too much light can damage the retina in your eye. This happens when you look at something which is very bright. One such example is the sun. Although the damage can heal, there are some cases where the situation is very bad. It will be permanent if you stare at the light for too long.