Heart of Quantum Physics

The Heart of Quantum Physics

The heart of quantum physics lies in the “dual nature of atoms”. In quantum physics, an atom can have a particle or wave nature. This theory is in particular called the “wave-particle duality of atom.” Various experiments have already been conducted to prove this theory correct. Quantum physicists explain this dual nature and properties of atoms using light as an example.

The figure below demonstrates that light comes out in waves. As the light hits the first screen, it squeezes through the two slits and spreads out on the second screen. The spreading out on the second screen is called the “interference pattern” (also called “diffraction pattern”). “Interference” means the intermingling or mixing of two or more different things and events.

What happens when two or more waves intermingle with each other? What happens when two or more waves intermingle with each other?

Now, throw another pebble in any direction away from it. What happens? You will notice the same formation you saw when you threw the first pebble. But that’s not all. You will notice that the two formations will eventually merge and form one new formation.

You can throw another pebble as many as you can and you will notice that as a new pattern of formation emerges, all these separate and isolated formations eventually merge to form one new interference formation. Remember that we are demonstrating this dual nature using light and this is how light behaves as a wave.

This time we will use atom or any one of its sub-particles. First, we will shoot atoms into a one-slit screen using a laser gun. We cover one slit and fire a stream of atoms through a beam gun. When atoms hit the screen, they arrive on the second side of the screen, spreading and overlapping each other, but do not produce an interference pattern.

We see in the interference pattern arriving randomly on the other side of the screen. But as one keeps sending atoms one at a time, the same wavelike pattern appears. This is how waves behave.

But what happens if we open the second slit so that particles will have to squeeze each other and enter either one of the slit? This time an interference pattern appears on the second screen, like what we got with light.

Let’s do another experiment. This time, we will send the atoms one at a time, rather than sending the atoms all at once to get through the screen. We see an interference pattern forming on the second screen, like what we got with light. The atoms have gone through the slit like waves. This is how waves behave.

This time an interference pattern appears on the second screen, like what we got with light.  We see in the interference pattern arriving randomly on the other side of the screen.  But as one keeps sending atoms one at a time, the same wavelike pattern appears. This is how waves behave.

What happens: (1) when no one is observing the atoms; and (2) when one is observing them passing through the slits?

When unobserved, atoms behave like waves and not like particles. When observed, atoms behave like particles and not like waves.