What are Quanta?

Quanta are “lumps” of light, and they were first described in 1901 by the German physicist Max Planck (who now has a telescope named after him). He was studying the radiation from black bodies and came to the conclusion that electromagnetic energy is emitted in packets. This idea was the basis of one of the most fundamental theories in physics – Quantum Theory.

When a light source gives out energy, it loses this energy in invisible packets called quanta. Einstein went further. He said that this energy was converted into separate packets of energy called photons, which carry the energy of light and other magnetic radiation.

Every form of energy comes in “bits”, or quanta. Imagine you have a lamp at home and connect it to a dimmer, you might think that when you turn the knob the fade is smooth and continuous. Actually, you’d be wrong. Your eyes aren’t sensitive enough to detect it but the decrease in brightness comes in steps.

There’s no such thing as a truly smooth fade because energy comes in chunks. The world is digital not analogue.

In the case of the lamp: say it looses 100 quanta a second, which it does by emitting 100 photons a second (this is just for the sake of argument – 100 photons a second is so dim you probably wouldn’t see anything). Now, as you turn the dimmer switch, the light fades because it is losing fewer quanta a second so is giving out fewer photons. As you turn the dimmer, the number of photons is gradually reduced until you come to the very last one, and then the light goes out. The whole point of this exercise is to show that energy is not smooth, it comes in packets, and these are called quanta.