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Light, Colour and Polarisation
Whatever we love and enjoy in life, we could rarely appreciate it without light and colour. As well as allowing us to see the beauty of the world around us, it is light from the sun that allows plants to grow and feed us. But what exactly is light made of? And where do the different colours come from?
Light travels like a wave. A red light wave travels slower than a blue light wave, and our brains percieve the different speeds as colour!
Polarisation describes the direction that the light wave is vibrating. An undisturbed light wave will be vibrating in random, constantly changing, but different mediums and filters can polarise light in different ways, by restricting the directions which it can vibrate in. This means that the light coming out the other side will be different than that which went in.
A wide variety of filters exist, which can polarise light in very different ways. For instance, some are designed to filter out specific colours of light. When two polarisising filters are placed atop one another, they can be transparent (see through) or opaque to light. By rotating one of the filters by a quarter turn, the light passing through can be turned ‘on’ or ‘off’. When the filters do not transmit light, they are said to be ‘crossed polarisers’. This happens because one is only letting horizontal light through and one, vertical. Placed together, and no light gets through at all! Certain materials such as cellophane tape and stressed plastics exhibit beautiful colours when placed between two crossed polarizing filters!
This clear tape dispenser in polarising the light traveling through it!
Some good web links to try: http://polarization.com/
