Physics: Wave-Particle Duality
When you think of light do you think of it as a particle or wave? It turns out that light behaves like both thus leading to the concept of wave-particle duality. So first lets start out with the fact that light can behave like a wave. Well, light is a type of electromagnetic wave, it has oscillating electric and magnetic fields(hence where the name comes from). These fields are at right angles to each other.
Like any wave light has amplitude, frequency and wavelength. For example red light has a wave length somewhere between 620 and 700 nanometers. Blue light has a wave length between 450–500 nanometers. The color of light varies with its wave length and frequency.
Another way light behaves like a wave has to due with the diffraction patterns it can form. Lets say you have two slits and a screen at the back. If you were to shine a source of light to the left of those two slits, you will see the diffraction pattern of the light. As these waves interact with the openings they will diffract. As these waves bend around the opening they create an interference pattern.
There will be areas where its bright and areas where it is dark in an alternating pattern. The areas where its bright represents constructive interference. Constructive interference occurs when the wave or the two interfering waves are in phase of each other. This results in them to reinforce each other so the amplitude is doubled. The dark spots represent destructive interference which is when two waves cancel each other out(they’re out of phase). Only waves can show this behavior, hence this is proof that light can act as a wave.
But now lets move on to how light can act like a particle! Light can be seen acting as a particle in the photo electric affect. So lets say you have a piece of metal and you shine blue light on it. Blue light has enough energy to eject electrons off certain metals. The ability of a photon to eject an electron depends on the frequency. Red light doesn’t have enough energy(high enough frequency) to eject electrons from certain metals but blue light can. The fact that light has ability to knock off electrons from a metal, it shows that light behaves like a particle.
This has led to the idea of wave-particle duality as we have seen that light has a dual nature. It could behave as a particle known as a photon and these photons can act like waves as they can form diffraction patterns around two openings. Electrons also behave the same way! They also have a dual nature as they can behave like particles and waves. If you were to blast a string of electrons around two openings it can form a similar interference pattern to the one mentioned above. The difference between and electron and photon is that an electron is a charged particle whereas a photon is neutral.
