Last night, I quickly had a look at the weather forecast for today. It confidently reassured me that there would be a bright, sunlit morning with a 5% chance of rainy spells. Of course, I had no doubt in my mind that the forecast was telling the truth. In the morning, I awoke with a large yawn and a badly-needed stretch. As I got up to draw back the curtains and admire the sunshine, I felt a sharp chill creep up my spine. “Hmm, it’s oddly cold in here”, I thought. Throwing back the curtains in vivid anticipation, my eyes flinched at the glare. My garden was covered edge to edge in a thick layer of bright, white snow. Just as predicted, right?
Before the 20th century, light was thought to be a wave, and classical wave theory could describe its properties and its behaviour. However, the works of various physicists, most notably Max Planck, Albert Einstein and Erwin Schrödinger, found light to possess particle-like properties also. The idea that light could possess both wave-like and particle-like properties, named wave-particle duality, did not agree with classical physics. A new set of theories were required to explain such unusual behaviour, and thus came the birth of quantum mechanics in the early 20th century.