One of my more favourite things to talk about is the electromagnetic spectrum, but to understand what the electromagnetic system is, you need to understand light. Ask yourself, what is light? Can you come up with an answer that doesn't involve the word sun in it? The Sun is a good place to look for light, as it provides the planet with lots of it.
Over the span of hundreds of years, many philosophers and physicists would question the properties of light, such as how it passes through glass yet not a thin piece of wood. What is darkness in relation to light? What would the material world look like or appear to us as without light bouncing off solids and passing through liquids? Questions similar to these were asked around the 1800’s, creating a big division in physics that many renowned scientists got involved in. It was the question: Is light a wave or a particle? Some may know the truth, but not quite the understanding behind it, and how it came to be. I will explain what a wave and what a particle is, as well as giving the answer that was sought after for hundreds of years in a bloody conceptual war between physicists over the infamous question.
Go with the Flow
(Figure 1: Diagram of a wave function.)
When talking about waves in physics and mathematics, they are not waves from the ocean, but rather a disturbance that travels from one medium to another. This disturbance carries energy, but not in clusters of particles, rather like a fluctuating beam of energy that is oscillating up and down as it moves forward in direction. In Figure 1 above, this diagram gives a good pictorial explanation as well as key parts to wave (but we won’t worry about those today).
When physicists applied this knowledge of waves to light, and did an experiment called the Double Slit experiment, light acted as a wave.
The Double Slit experiment involves shining light onto a wall, and placing a piece of paper in front of the light source to block it. On this paper are two exactly same slits, allowing a small amount of light to be shone onto the wall. When applied, the light would have patterns of shadow and light, similar to the ripples of water when two objects enter the water at the same time. These ‘ripples’ were called interference patterns, because when light acted as a wave, some waves would cancel each other out and cause a shadow in place of light, a diagram of this is in Figure 2 below.
(Figure 2: Diagram of the Double Slit experiment.)
So surely the answer was found, and the matter can be put to bed? A physicist by the name of Heinrich Rudolf Hertz decided that it wasn’t, because he found an interesting phenomena which proved light is a particle.
In Electric Shock
In simpler terms, a particle is a very small block of matter, whether it be an electron or an atom. The photoelectric effect, discovered by Heinrich Hertz, is the ejection of particles from a metal plate when any type of light falls upon it. The idea is that light is made of particles called Photons, and when shining light onto a metal plate, these photons knock the electrons off, which in turn makes a noticeable ejection rate. Figure 3 below depicts this well.
(Figure 3: Diagram of the Photoelectric Effect.)
Two is better than one
Alright, so now we have two very different experiments in which one proves that light is a wave, and another that proves light is a particle. What to do now? If we go back to the Double Slit experiment, it also proves that light is a particle. When the frequency of light is lowered to allow only one photon each to go through the slits in the screen, it makes a single, point-like mark, indicating that the photon interacted as a particle. With this confusing breakthrough, the most obvious (and very weird) conclusion was that light is both a wave and a particle. Einstein believed light is a particle (photon) and the flow of photons is a wave. The main point of Einstein's light quantum theory is that light's energy is related to its oscillation frequency. And by frequency it means the rate of ups and downs (oscillations) in a wave length.
So that was that, or was it really? To this day there are still many questions about light, and the electromagnetic spectrum of light that remain unanswered.
Thank You for taking the time to read this blog, and supporting my adventure into science and maths. I also advise to not take my words as your only source of information, please cross-reference and leave a comment if you believe something was incorrectly stated. My main reference would be to a book I am currently reading called The Strange Story of The Quantum by Banesh Hoffmann. It tells the tale of light and quantum discoveries in an entertaining and non-mathematical way.
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