Playing around with light

The front cover of the Pink Floyd album Dark side of the Moon famously features a Prism.
Shine white light in one end and the colour spectrum comes out the other end. Prisms reflect and refract the light through them much like luxury chandeliers from company’s such as why do they do that?

First what is a Prism? Simple it’s a “transparent optical element”. It has surfaces that are polished up and perfectly flat. For the prism to work the sides must be angular and the best shape for that is a triangle like the one in the Pink Floyd album.

This is a pyramid shape with flat base and the sides pointing up to a point. The surprising thing about the Prism is that whilst you may think that glass is the only thing that does it.

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However it can be anything transparent and at the right kind of angles. It doesn’t even need to be a solid, water is quite capable of doing it and on a grand scale such as with a rainbow.  It is easier to achieve with a solid though and glass does lend itself better than most. Plastic can happily Crete the same effect and the crystal fluorite is usual cut and shaped specifically for this purpose.

When you see light in general it is white light. What the Prism does is refract the light. What refract means is to spilt the light up so that we can see the all of the colours that make up the light. As we are as we are dispersing the light with the Prism unsurprisingly called a dispersive Prism. We call these other lights spectral colours. So, know we know what the prism does and what everything is called let’s look at why it does it. That might be a little bit harder to explain.

You know about the speed of light? It’s pretty much instantaneous. It goes so fast that it appears to us a constant thing in our vision. Light can change sped when it moves through different mediums. The Prism in this case is the medium.

When that speed changes the light starts to refract to show its going at a different seed. Again, this seems to be instantaneous to us. It doesn’t make a Brummel sound or anything like that, it just is. The angle of the where the white light shines in will also affect the refraction of the light.

Also, the material that the lights shines through will make a massive difference to the quality and the clarity of the refracted light that shines through the other end. The scientist you can thank for discovering this was Sir Isaac Newton, who discovered many things. Up to that point it was believed that light was colourless.

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