Have you ever wondered what quantum physics was all about? Grab a tray of water and learn a bit about the strangest science of the twentieth century!
A wave is a pattern that moves through something. Think about a Mexican wave at the cricket or the wobbling of a plate of jelly. Without the people or jelly, there is nothing to wave.
Waves come in different forms, depending on how they move. In the water they are called ‘transverse’ waves, and they move up and down in the direction they are travelling. The highest point is a crest, and the lowest point is called a trough.
When a wave hits the slot, it ‘diffracts’ through it. This means it bends around the corner, rather than simply continuing through in a straight line.
The spray bottle, on the other hand, shoots out a stream of small particles. The image cast on the paper is roughly the same shape as the slot – the spray did not ‘diffract’ through the slot like a wave.
Throughout history, a number of scientists have had opinions on what light is made from. Is it a stream of tiny particles? Or is it made of waves rippling through something, just like sound through air or the swell of the ocean?
For many centuries most scientists, including Isaac Newton, argued light was made of particles. Since light makes shadows just as with the spray bottle, it cannot be a wave.
However, light sometimes does behave like a wave. When two waves meet, they combine, like waves at a beach. Should the crests line up, the wave will get bigger. But if the troughs and crests meet each other, they can cancel each other out and make the wave disappear. This is called an interference pattern.
While light creates shadows, it also diffracts around corners, and experiments show that light will also form interference patterns like any other wave.
Yet waves need something to ripple through. It was once suggested that a gas called aether fills the universe, allowing light waves to move through space. Yet no evidence of such a material has ever been found.
So, is light a wave of something smaller? Or is it a particle?
Oddly … it is both. This is referred to as the ‘wave-particle duality theory’. Stranger yet, all matter, on the smallest scales, is also formed by tiny waves in a strange, universal ocean.
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