One Finite Planet

Photons: What is electromagnetic radiation?

First Published:

Radio waves, microwaves, millimetre waves, infra-red, visible light, ultra violet, x-rays, gamma rays…
…… can seem so different, yet they are all electromagnetic radiation.

All are composed of the same fundamental particle: the ‘photon’.

All photons, travel at the ‘speed of light’ (or the ‘speed of photons?’), have the properties of a wave, and interact with electrons.

Photons can be absorbed by an electron, and when this happens, the electron takes on additional energy, and with sufficient additional energy electrons move to a higher energy state. Electrons can then release energy and drop back to a lower energy state, emitting a new photon when they do.

This cycle of being absorbed by electrons, and emitted by electrons, is the main interaction between photons and other things. It is the basis of how we see, how heat is radiated, how radio signals are transmitted and received, and how microwave ovens work. There are countless photons everywhere, being absorbed, and being

Every ‘photon’ has carries a specific amount of energy, which determines the ‘frequency’ of that photon. The total extra energy delivered to an object by a stream of photons is the energy per photon multiplied by the number of photons. Any object with energy will also be radiating some energy out by emitting photons. So an object which is otherwise stable, will either gaining energy, which will most often indicated by an increase in heat, or lose energy, typically be getting cooler, depending on whether there is more energy in the photons being absorbed, or more energy in the photons being emitted.

In considering energy arriving from absorbed photons, a useful analogy to consider bullets being fired at a wall. You can deliver the same total force to the wall by either doubling the number of identical bullets, or doubling the mass for the same number of bullets. If the bullets are so small they just bounce of the surface of the wall, then increasing the number of bullets will still result in all the bullets just bouncing off, even though the total push against the wall has doubled. Similarly, while doubling the number of identical photons will increase the energy or heat delivered, if those photons do not do enough to the electrons to change the structure of the molecules, receiving more photons still will not change the structure. This is why the frequency of the photons is so important. It is not just the total energy that determines the impact, it is also the power of the individual photons.

Note that 1Mhz is 106 Hz, 1Ghz = 109 Hz, 100Ghz – 1011 Hz etc.

Generally, individual photons with an energy much higher than visible light are considered ‘ionising photons‘. While photons below this energy level can make us feel warm, photons above this energy level can damage our cells. We definitely know that higher energy UV, or X-Rays or Gamma rays can cause cancer. We aware of no side effects visible light photons at the level we experience on a sunny day, and generally it seems that this same number of photons, or less, at even lower frequencies should pose even less risk. However there is always the risk of something we do not know. In terms of risk, the higher the frequency the photons, the more care warranted in ensuring the quantity is not too high.


Table of Contents


Surprise, Shortest day ever recorded surprises: Not the solstice!

This page is more under the heading of ‘fun facts’.

The first ‘fun fact’ is that while everyone knows how the length of daytime and nigh time vary throughout the year, it may come as a surprise to realise the length of the entire day, also varies. Partly because, second fun fact, the a day is a longer than one rotation of the Earth, which lead to the third fun fact: we just had the shortest total day ever recorded.

Read More »

Carbon Capture and Storage: When it works, and why it doesn’t for work ‘blue hydrogen’.

There are both vocal supporters and vocal opponents of carbon capture and storage, and there are arguments for both sides. This page goes beyond reporting on how carbon capture and storage fails to make current ‘blue hydrogen’ projects sustainable, and looks at the underlying principle that dictates why carbon capture and storage, despite having genuine valuable applications, can never enable ‘blue hydrogen’ to be environmentally sustainable, but is so popular politically.

Read More »

Covid-19 & Vaccination Deaths: Statistically, Coincidences will distort reported deaths.

I read recently about reasonable people protesting over post vaccination deaths in South Korea, echoing stories from around the globe about the underreporting of deaths following vaccination.

Can most of these deaths be just coincidences? This question has me seeking the real story on what is happening, not just with deaths following vaccination, but also with deaths from the virus. Almost one year after my initial exploration of vaccine efficacy and safety, now there is data, not just projections, so it is time for a review, and this question needs answering for any such a review.

Read More » to the Next Level: Plugins, Elementor, CoBlocks?

Something completely different. A discussion on how this site is hosted: on

Anyone who has started a “blog” or other site on, may get to wonder, what are the options for upgrading the website? What is the value of the free, personal or premium plans and beyond? What real world benefits are there, and, alternatively, what would you lose and/or gain from moving away from This is a page discussing being in that situation. If you are not considering having a website, it may be of little interest.

Read More »