⇒ We had a look at electromagentic waves when discussing the topic of Waves

⇒ Some of the lower frequency electromagnetic waves, such as radio waves, microwaves, infrared, and visible light, don't have enough energy to cause any serious problems (they just pass through things really)

⇒ When you get to the higher frequency end of the electromagnetic spectrum, such as ultraviolet, x-rays, and gamma rays, those can cause some issues because they do carry with them quite a lot of energy

⇒ The low end of the ultraviolet spectrum is not what we call ionising, however the higher end is ionising

⇒ Ionising radiation can knock electrons away from atoms, which causes ions

• Ions have different properties to their standard atom counterparts, which can cause issues

⇒ So the problem with ultraviolet waves is that some of these waves are ionising

⇒ The sun, for example, does give off a lot of ultraviolet radiation, which can potentially cause skin cancer and premature aging

• This is why you need to wear suncream when you go outside, as this will block the ultraviolet radiation from reaching your skin

⇒ X-rays are useful for seeing inside people for non-invasive imaging as they go through soft-tissue but are absorbed by bones

⇒ So x-rays and gamma rays are particularly dangerous - gamma rays more so than x-rays

⇒ Ionisation from x-rays or gamma rays could cause gene mutation, tumours to form, and other potenailly harmful effects

• Most of the time when these things happen (e.g. when there is a gene mutation), that cell will die
• But if the cell doesn't die, it could replicate and form cancer

⇒ We can measure the risk associated with a particular dose of ionising radiation using a unit called sieverts

⇒ Sieverts is a measure of risk of harm from radiation exposure

⇒ This doesn't technically have to be from electromagnetic radiation, as it could be from other ionising things like alpha and beta particles

⇒ A NASA astronaut will be subject to, at the absolute most, 1 sievert of risk over their entire career

⇒ Because 1 sievert is so much, it is often measured in milli-sieverts (mSv)

⇒ Whenever you go for an x-ray at the hospital, the doctors will weigh up the risks/benefits to see if it is worth giving you an x-ray knowing the potential it has for harm

⇒ A lot of the time they will give the go ahead as they can minimise the risks in a number of ways, but they will have to take the risks into account

⇒ Also see our notes on:

• Electric Current
• Current, Voltage and Resistance
• The Dynamo Effect
• Power Stations
• Electrical Power
• Waves - The Basics
• Waves
• Refraction
• Uses of Waves
• Analogue and Digital Signals
• Wind and Solar Energy
• Seismic Waves