waveâparticle duality

How do we know light is a wave?

Before I answer this question, I’ll need to briefly go over a wave property called superposition. Basically, superposition is the idea that two waves can be in the same position at the same time, and interfere with each other:

When the two waves add to each other and make a larger wave, we call this constructive interference. When the waves cancel each other out, we call this destructive interference. 

Now we’re going to move on to the Double Slit Experiment. Basically, you shine a beam of light at a piece of metal, cardboard, etc with two slits in it, with a surface behind it where you can see the light hit it. 

If light is a wave, what we’d expect to see would be an interference pattern created by the light from the first slit interfering with light from the second slit, which is exactly what we see. It’s a pattern of constructive interference (brighter regions) and destructive interference (darker regions), looking like this:

These images are helpful:

that is how we know light acts as a wave!!

Illustration of Wave Particle Duality.

Wave Particle Duality is one of the most astounding discoveries ever made. Light behaves as a Wave when it is not observed but behaves as a Particle when observed. We all Vibrate through the Structure of Space-Time and we make Waves just like Photons. So are we Particles or Waves? We are Both. Observation Creates your Reality. Math and Art blended as one and the same, Pure Geometry.

Equation #11: Heisenberg’s Uncertainty Principle

Anyone who is not shocked by Quantum Mechanics has not quite understood it”-Niels Bohr

I agree Mr. Bohr, QM does blow your mind. The uncertainty principle is one of those things that prove that our perception of the world is limited. Anything in the universe can be both wave and particle at the same time and that puts a limit to how accurate our measurements can be.
What that means in our context is that, if you try to measure the velocity(or momentum) of a particle as well as its position at the same instant, you cannot have exact values of both. If you measure position accurately, the value of velocity will have some uncertainty associated with it and vice a versa. 

The reason we don’t observe this phenomenon in everyday life is is that the uncertainty values are very, very tiny. A person moving with a velocity of say, 5 km/hr (+or - 0.05 km/hr) and weighing 60 kg will have the uncertainty in position = 1.8 * 10^-35 meters! That’s smaller than the radius of an atomic nucleus. However, when you go into the realm of lightweight, superfast entities(like subatomic particles), the uncertainties get larger and can have a significant effect on the macroscopic properties of an object. 

The uncertainty principle applies to a number of pair of observables other than momentum and position. Most common example is that of energy-time which explains the working of Strong force, according to some theories.

It is important to understand that this fundamental limit is not due to experimental errors, rather a phenomenon of nature itself.

You cannot predict, even theoretically, the exact values of two so called “incompatible” quantities simultaneously.

For uncertainty principle in action, see

For more clarification, see



Ask Ethan: do gravitational waves exhibit wave-particle duality?

“We’ve actually got a few chances for this, although LIGO is unlikely to succeed at any of them. You see, quantum gravitational effects are strongest and most pronounced where you have strong gravitational fields in play at very tiny distances. How better to probe this than for merging black holes?! When two singularities merge together, these quantum effects — which should be departures from General Relativity — will show up at the moment of the merger, and just before (at the end of the inspiral) and just after (at the start of the ringdown) phases.”

Now that gravitational waves have been verified to exist, and the first black hole-black hole merger has been definitively detected by LIGO, it’s time to start thinking of the next steps in gravitational wave astronomy. The biggest one we can dream of, perhaps the holy grail of this field of study, is to go beyond General Relativity itself, and to find evidence that gravitation is a truly quantum theory at its core. If that’s true, then these gravitational waves should exhibit wave-particle duality, just like all the other quantum entities we know of. In this case, detecting the wave-like phenomenon, which took a century to do, was the easy part; detecting the particle nature of gravitons will be the hard part. Nevertheless, even though this is likely beyond the reach of LIGO, future missions will have a chance to see these quantum effects down the road.

Wave particle duality is a core feature of our world. Or rather, we should say, it is a core feature of our mathematical descriptions of our world. But what is critical to note here is that, however ambiguous our images, the universe itself remains whole and is manifestly not fracturing into schizophrenic shards. It is this tantalizing wholeness and the thing itself that drives physicists onward like an eternally beckoning light that seems so teasingly near. It is always out of reach.
—  Margaret Wertheim

Finding quantum mechanics in a cup of coffee. This is a great video from Sixty Symbols featuring an atomic-scale sculpture and an interesting experiment with a cup o’ joe.