There is no need to fear electromagnetic radiation

By MUNGAI KIHANYA

The Sunday Nation

Nairobi,

20 July 2025

I find that many people are comfortable with the idea that the pitch of a sound is directly related to the frequency of vibration, but not so with the colour of light. Perhaps it is because when sound is being produced, we can see something vibrating; for example, the cone of a loud speaker. We can also feel our voice box vibrating if we touch it while talking.

But when it comes to light, things are not so obvious: the evidence of its wave nature only becomes apparent to people who study post-secondary school science. And even then, not everyone of them!

Now the range of human hearing is very wide. It ranges from vibrations of 20 to 20,000 cycles per second (cps). But this is for young children only. As we grow older, it deteriorates due to over exposure to very loud sounds, especially during our late teenage and early adulthood. Think about matatu and club music as well as earphones.

My ears cannot hear sounds below 100cps or those exceeding 10,000cps! Still, this is a very wide range covering three powers of tens – from hundreds to tens of thousands.

Light is a different phenomenon. It is made up of electric and magnetic fields vibrating in unison. For this reason, light is termed as an electromagnetic radiation. Different colours of light will be waves of different frequencies. Our eyes can only see between 400 trillion (red) and 800 trillion (violet) cycles per second. Compared to the range of hearing, the one for seeing is very narrow! The highest frequency is only double the lowest; but in sound, the highest is 10,000 times the lowest.

Now, the name electromagnetic field or electromagnetic radiation may appear fearsome. This fear is unwarranted but understandable. There are some dangerous electromagnetic radiations. These are the ones with higher frequencies higher than visible light; including, the so-called ultra violet (800 trillion to 30,000 trillion cps), X-rays and gamma rays (billions of trillions of cps).

The radiation with frequencies below the visible range is safe. Here we have infra-red which vibrates at between 300 billion and 400 trillion cps (we feel it as radiant heat); microwaves – 300 million to 300 billion cps (used in ovens bearing the same name); and radio waves – below 300 billion cps.

FM radio broadcasts use 88 million to 108 million cps, which is also stated as 88MHz to 108MHz. MHz stands for mega-hertz or millions of hertz; “hertz” being the international name for cps. Evidently, there is harmless electromagnetic radiation all around us and therefore, there is no need for fear!