Proving the Wave Nature of Light the DIY Way! Young's Double Slit Experiment.

Ever since Newton's time, it is debated whether light is a wave or a particle. Grimaldi, Huygens, Maxwell said that light behaves like a wave, while scientists like Newton and Einstein said that light has a particle nature.

It was later established that light has a Dual nature. It acts both as a wave, as well as a particle.

With further research Louis de Broglie proved that there are particles (electrons, protons and neutrons) besides photons that have the properties of a wave.. According to de Broglie, all particles traveling at speeds near that of light adopt the properties and wavelength of a wave in addition to the properties and momentum of a particle. He also derived the relationship

"wavelength x momentum = Planck's constant."

This groundbreaking work is central to modern quantum mechanics and is an example of particle-wave duality.

Young's Double Slit Experiment is an excellent way to prove the wave nature of light.

This experiment was first conducted by Thomas Young in 1801, where he used sunlight reflected off a steering mirror passed through a small hole in a paper, and the resulting thin light beam was then split in half alongside a paper card. He then compared the resultant light pattern to the waves of water, and explained how water waves would make a similar pattern if passed through similar slits, which concluded his experiment and gave evidence of wave nature of light.

Here we will create our own double slit experiment and witness the wave nature of light ourselves.

Materials needed:

1. Laser pointer

2. Sharp pin

3. Aluminium foil

4. Tape

5. A really thin wire (or in my case, a strand of hair)

Cut a piece of aluminum foil enough to cover the aperture of the laser pointer, and tape it down on the laser as shown.

Turn the laser on and make sure that laser is not shining through the foil. If it does, your foil might have holes, change it or tape another piece of foil on top of it.

Use a sharp pin and puncture the foil in the center.

Try to be as still as possible, so that the hole is clean.

Now, we will try to tape the thin wire or strand of hair right in the centre of the pinhole.

Tape down the piece of hair on one end of the laser, stretch it to the other side trying to get the hair right in the middle of the pinhole. secure the wire/hair in place with some more tape.

The strand of hair now divides the pinhole into 2 different light sources.

Shining the laser with the two slits now produces the interference pattern similar to what Young observed.

Try pointing the laser pointer to a non shiny surface, like paper and keep it at least 2 meters away from the surface.

We now have a pattern of light very similar to a pattern we would find on a wave, where we can see constructive and destructive interference clearly.

This proves that light also has a wave nature.