not just described, Explained


Contact us

Misconceptions quiz

Subscriptions FAQ




Physics subscription prices

subscribe log in



Work and Money

PSHE subscription prices

subscribe log in

Lesson 1: Why study radioactivity?


In this lesson we introduce some of the uses of radioactivity and also some of the ways that it can be harmful.  We'll see how nuclear radiation is similar to other forms of radiation and also important ways that it differs.

Try Why Do Astronauts Float by Julian Hamm

Uses of nuclear radiation

Nuclear radiation is used in areas as diverse as medicine and engineering, for example: diagnosing and treating disease, finding cracks in concrete structures, monitoring the flow of rivers, measuring the thickness of paper and kitchen foil, sterilising delicate medical equipment, finding the age of ancient remains and preserving food.

The ways nuclear radiation can be harmful

Nuclear radiation can damage our cells causing burns, sickness, diarrhea and vomitting, infertility and sometimes death.  Small doses can damage our DNA which can lead to cancer when we're older.

What the words mean: radiation, radioactive, nuclear radiation

 Radiation is a fairly flexible word.  We can say that a light bulb radiates light, a speaker radiates sound or a mobile phone radiates microwaves.  Radiation is all about sending energy out into the surroundings.  This is often in the form of a wave but can also be little particles.

If something is radioactive then it sends out radiation that you can't turn off or affect in any way by any normal means.  If something is radioactive then the type of radiation it gives off is called nuclear radiation because it comes from changes in the nucleus of atoms.

Radiation tends to spread out in the surroundings

You can't get rid of energy but it does tend to get spread thinner and thinner and become impossible to detect.  This is what happens to all radiation in the end.  The energy gets spread so thin that you can't tell it's there any more.

If the radiation consists of particles then these particles don't disappear but they do stop moving.

Detecting nuclear radiation

You need special apparatus like a Geiger counter to detect nuclear radiation.  You can't see it, hear it or feel it.

You can use a Geiger counter to show that nuclear radiation is given off in all directions by something that's radioactive.

Irradiation doesn't make something radioactive

When nuclear radiation hits something, like an apple, we say the apple has been irradiated.  Irradiating things doesn't make them radioactive.  The apple may absorb the energy of the radiation, making it a little warmer, but the apple doesn't start giving off nuclear radiation.

Irradiation can be used to kill bacteria in food so it will last longer.

Nuclear radiation can't be increased, decreased or turned off

Non-nuclear radiation can normally be changed or even turned off.

But whatever we do we can’t change how much nuclear radiation a radioactive source gives off.  The only thing we can do is wait.

We can cool it down, heat it up, blow it to bits or dissolve it in acid but we never destroy the atoms themselves so we never change the amount of radioactivity.

We call something that gives off nuclear radiation ‘radioactive’.  So if something is radioactive we can’t turn it off!

Nuclear radiation: difficult to detect, impossible to change

Nuclear radiation can’t be seen, heard or felt and we can’t do anything to change it.  So there are two major reasons for making sure radioactive substances are carefully controlled.

Without special instruments you can’t tell that nuclear radiation is there until you notice the harm it is doing and this might be years later.  And you can’t change the amount of radiation given off so all you can do is keep the radioactive substance in a safe place.

Back to Summary of Radioactivity and Atomic Physics Explained