Uses and Dangers of EM Waves

Electromagnetic (EM) waves are all similar; they are all transverse waves that travel at the same velocity and are created by the movement of electrons. But they are also different, not only in wavelength and frequency but also in how they are reflected, absorbed or transmitted by different materials.

For example, the microwaves that your smartphone uses can go through solid walls but visible light is absorbed and reflected by those same walls even though they are both examples of EM waves.

The things that make EM waves different are the same things that make them useful for different applications. Clearly you would not make a smartphone that communicated using visible light because it wouldn’t work unless you could see the cellphone tower. But we do use light in optical fibres for high-speed broadband communication: why is that?

The answer lies in the fact that higher frequency waves can carry information at a faster rate (more information per second) and the frequencies of visible light are much higher than the frequencies used for even the best modern smartphones.

Nevertheless, this does explain why smartphone technologies generally need higher frequencies to deliver faster connections with better streaming, as indicated below.

Of course, there is much more to mobile communications than just frequencies (antenna design, for example) but the frequency is important and it is also the thing that people worry about when expressing concerns over the possible health issues associated with mobile phone masts.

One reason why people are worried is because microwave cookers use a similar frequency (typically 2.45 GHz) to those used by current smartphones. So some people think that holding a smartphone next to your head could “cook” your brain (or start cancerous growths).

It would be nice to say that this definitely isn’t true but all we know at the moment is that there is no definitive link between smartphone use and any adverse health effects. If you are interested in this topic then the two sides of the argument are nicely presented on these two websites from the American Cancer Society and radiationhealthrisks.com.

What we do know is that EM waves with higher frequencies than light carry enough energy to cause health problems of various sorts.

The examination board is very keen that should know about the uses and dangers of different types of EM waves so your next task is to compile a summary that lists the seven different categories of EM waves, together with some example uses and possible dangers for each type.

In the case of visible light, for example, your answer could be something like this…

Uses include; human vision, television, optical astronomy, car headlights, photography, etc. The dangers are few except that a burst of extremely bright light could cause blindness, which may be temporary but could be permanent. The frequency of the wave is not enough to cause danger at normal light levels but if the amplitude is increased massively then damage may be caused to any device (including electronic systems as well as the human eye) that is designed to operate at normal light levels.

For more information, use online research and also read your CGP Revision Guide, pages 78-82.