Observing nuclear radiation

STARTER ACTIVITY:

* List some things we can not see and how we detect them:

Invisible things How we detect them

Infra-red radiation Face, cheek, thermometer

Wind Damage it leaves behind

Nuclear radiation Damage it leaves behind ??

Lesson objectives; You will learn:1. Structure of the atom2. Why some nuclei decay3. The 3 types of radiation

Observing nuclear radiation

1896 Henri Becquerel: Some photographic paper in a sealed bag was fogged but had the image of a key on it.

He deduced that some form of radiation from the uraniumrocks had passed through the paper but not the metal key.

Observing nuclear radiation

Marie Curie, a research worker said these rocks were “Radioactive”* the rocks gave out the radiation all the time* chemicals and heating made no difference

She discovered a new radioactive element polonium.She died in middle age of Leukaemia.

Q.You can stop a light from giving out light radiation.

Is it possible to stop uranium giving out nuclear radiation?

Why are some substances radioactive?

Some atoms have an unstable nucleus and need to get to a lower energy state.

It can become stable by emittingAlpha, Beta or gamma radiation. It “decays”.

A decay is a random event -it happens without anything being done to the nucleus.

The structure of the atom

ELECTRON – negative,

mass nearly nothing

PROTON – positive,

same mass as neutron

(“1”)

NEUTRON – neutral,

same mass as proton

(“1”)

The structure of the atom

-10Electron

01Neutron

11Proton

Relative ChargeRelative MassParticle

MASS NUMBER = number of protons + number of neutrons

SYMBOL

PROTON NUMBER = number of protons (obviously)

Types of radiation

1) Alpha () – a nucleus decays into a new nucleus and emits an alpha particle (2 protons and 2 neutrons – the nucleus of a helium atom)

2) Beta () – a nucleus decays into a new nucleus by changing a neutron into a proton and electron. The fast moving, high energy electron is called a beta particle.

3) Gamma – after or decay surplus energy is sometimes emitted. This is called gamma radiation and has a very high frequency with short wavelength. The nucleus is not changed.

Unstable nucleus

Unstable nucleus

Unstable nucleus

New nucleus

New nucleus

New nucleus

Alpha particle

Beta particle

Gamma radiation

Ionisation

When radiation collides with neutral atoms or molecules it alters their structure by knocking off electrons. This will leave behind IONS – this is called IONISING RADIATION.

particle

Electron

Detecting radiation

Gieger-Muller Tube

Spark counter

Photographic film

Cloud chamber

What are the different methods?

Photographic film

1. What happens to film when radiation is incident upon it?

It darkens.

2. Can photographic film tell you the type of radiation incident upon it?

No, just the amount of radiation received.

3. What can this be used for?

Can be used in radiation badges, that record the exposure of workers to radiation. Different windows detect different types of radiation.

Observing nuclear radiation