Top 10 Greatest Physics Experiments: 6. Newton's Prism

In number 6 we have another giant of physics – Isaac Newton. Newton is famous for his theories on dynamics of moving bodies, invention of calculus and the law of gravitation. However, not many people know that Newton also did many important experiments while investigating the properties of light.

Even though light is not completely understood even today, back in the 17th century, people actually new quite a lot. Ever since the times of Aristotle it was believed that light had some kind of a purest form (or colour), which somehow get’s altered to form other colours. It was believed that rainbows were somehow formed using this principle.

Newton decided to test this prediction by shining a ray of white light through a glass prism. And the result of this is one of the most beautiful experiments in the history of physics.

So what really happens is that white light, which is made up of all the main colours (Red, Orange, Yellow, Green, Blue, Indigo, and Violet) when going through the prism, splits up in the mentioned colours, all leaving the prism at different angles. This is due to the fact that light changes speed when entering a different medium like glass. This depends on a thing called the refractive index of a material, which is different for different colours and different materials. Thus all the colours that make up white light refract at different angles, which is exactly what causes a rainbow pattern to appear.  

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