Quantum Physics Part 1: Bit about Light Waves and the Electromagnetic Spectrum

So, quantum physics. Hear me out. Quantum physics is brilliant and not too difficult to conceptualise. Should probably go about it by splitting it up before we talk about cats and boxes.

Part 1: First little bit to know: light is a bit weird. If you ever hear “electromagnetic wave”, that is talking about light. Simply, light has an electric field AND a magnetic field. Skip to part 2 if you don’t care but for extra marks, know that those fields are perpendicular to each other and they are both perpendicular to the direction it travels in. Have a look at the world’s most diabolical drawing of that below (ignore any smudges), note that c refers to the speed of light and the arrows mean that those fields have not only a magnitude or size, but it’s also important to note that they have a direction:


I’ve tried to show that the red line is the electric field and is 90 degrees to that of the black electric field, and that together, it’s a light wave (woooo). This is what Mr Ray Ban uses to make his sunnies protect your retinas but we’ll talk about polarisation another time.

So far: Light is an electromagnetic wave. Check.

Part 2: Not all light is visible. Everyone’s heard of x-rays, microwaves (Rustler, anyone?) and radio waves, yeah? Sweet. They are different because they have different wavelengths/frequencies. Very quickly: Frequency is the speed of light divided by wavelength. Frequency being “how many times per”, so, how many oscillations per wavelength. See slightly better picture to see that wavelength is the distance between peaks (top bit of wave), the frequency might be how many wavelengths happen in 1 second. My point: we have different properties for waves because they all have different wavelengths – a statement that can be interchanged with “…because they all have different frequencies”.


TL;DR: Different names for electromagnetic waves because of the frequency that it oscillates.

Part 3: Next step has to be to discuss the different properties due to the different frequencies but very simply: higher frequencies have higher energies (more oscillations in the same amount of time) whilst high wavelengths have low energies (less full waves in the same amount of time). High frequencies are stuff like x-rays and gamma rays whilst radio waves as microwaves are low frequency. That’s why you can point a TV remote at your face and not die… The light we can see is in middle between being high frequency and low frequency and goes from the low energy colour of red all the way up to violet at the more energetic side. How do we get white light? When green, red and blue light combine to make….white? It does though, Sir Isaac Newton played about with some glass prisms and showed the light splitting up into the different colours. Pretty neat.

The lazy picture below shows infrared on the left and x-ray on the right. X-rays being of a high energy mean that you can’t point it at your face as you might die.


In short: The higher the frequency that light oscillates, the higher the energy of that light. Also, infrared is much less energetic than x-rays. X-ray can burn your face off because the wave is higher energy.

All this jazz is a basic attempt at describing the Electromagnetic Spectrum. First little bit: done!