Unit P2 - RadiationUnit P2 - RadiationLesson 01 – Introduction to RadiationLesson 01 – Introduction to Radiation

Aims:• Know that radiation is

produced from the nucleus of the atom

• Know that there are three different types of nuclear radiation

Questions…1. What particles make up

atoms?

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It comes from…

Sources of background RadiationSources of background Radiation

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Sources of Background RadiationSources of Background Radiation

Source Amount

Radon Gas from Granite 51 %

The ground 14 %

Food & Drink (coffee & peanuts)

12 %

Cosmic Rays (outer space) 10 %

Medical (X-Rays etc.) 12 %

Other (including nuclear power stations)

1 %

In the South West, radon gas is a major contributor to background radiation.

This is more evident in enclosed spaces e.g. caves and granite houses on Dartmoor

You are exposed to a lot more cosmic radiation on a flight.

What happens when radiation What happens when radiation reaches atoms and cells?reaches atoms and cells?

• Alpha (α) and beta (β) cause ionisation – the radiation removes electrons from atoms.

• This makes the atoms very reactive• It makes atoms react uncontrollably

making strange substances• It makes cells faulty – possibly

causing cancer• The higher the dose of radiation – the

greater chance of damage / cancer• Most gamma radiation passes

through people and does not cause much damage

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What happens when radiation What happens when radiation reaches atoms and cells?reaches atoms and cells?

• Alpha (α) and beta (β) cause ionisation – the radiation removes electrons from atoms.

• This makes the atoms very reactive and can…

• It makes cells faulty – causing cancer

• The higher the dose of radiation – the greater chance of damage / cancer

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It is detected by…

Geiger counter Geiger counter

Demo Geiger counter

Do some work…

There are three main

types of Radiation

Radiation – a few facts…Radiation – a few facts…

• The nucleus of atoms is made from protons and neutrons

• Radiation comes from the nucleus of atoms

• There are three types of radiation

Alpha α Beta β Gamma γ

α β γ

Alpha Decay…

• Phosphorous atom

(15 protons)

Proton

Neutron

Electron

Nucleus becomes unstable…

• Phosphorous atom

(15 protons)

Proton

Neutron

Electron

A group of 2 protons and 2 neutrons ejected…

• Phosphorous atom

(15 protons)

Proton

Neutron

ElectronThe group of 2 protons and two neutrons is called an ALPHA particle

It shoots out at high speed straight past the electrons

Alpha particle…

A group of 2 protons and 2 neutrons ejected…

Proton

Neutron

ElectronThe phosphorous atom has lost 2 protons (it now has 13)

It is now an Aluminium atom

Beta Decay…

• Phosphorous atom

(15 protons)

Proton

Neutron

Electron

Beta Decay…

• Neutrons are made from a proton and an electron (& an anti-neutrino)

Proton

Neutron

Electron

Beta Decay…

• A neutron becomes unstable, it splits up and ejects the electron at high speed. (the anti-nutrino is ejected)

• The proton stays in the nucleus

ProtonNeutronElectron

Gamma Decay

• When alpha or beta radiation is produced excess energy is released as a gamma ray

• Gamma rays are not particles

• Gamma rays are part of the electromagnetic spectrum

Types of RadiationTypes of Radiation

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

2) Beta () – an atom decays into a new atom 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 atom is not changed.

Unstable nucleus

Unstable nucleus

Unstable nucleus

New nucleus

New nucleus

New nucleus

Alpha particle

Beta particle

Gamma radiation Copy this bit…

IonisationIonisationWhen 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

Different Different radiation is radiation is

stopped by a stopped by a different different materialmaterial

RadioactivityRadioactivityIf a substance is capable of ALWAYS emitting radiation under any conditions we say it is ____________. There are three types of radiation: ALPHA, _____ and GAMMA. These types of radiation are always given off by rocks, _____, building materials, air and cosmic rays around us – this is called BACKGROUND RADIATION. Each type is capable of penetrating different materials:

Sheet of paper

Few mm of _________

Few cm of lead

Words – aluminium, beta, food, radioactive

Properties of alpha, beta and gamma radiation…

Name of radiation

Symbol Passes through:

Is absorbed by:

Alpha α 5cm air only A few cm of air

Beta β Air & paper A thin sheet of paper

Gamma γ Most things except thick lead and concrete

A thick sheet of lead

A very thick wall of concrete

Task…Task…1. Use longman FND

book 2 – Page 2342. Produce three bubble

map showing the properties of alpha, beta and gamma radiation.

3. Then, produce a ‘double bubble’ map showing comparing and contrasting the properties of alpha and beta radiation

Alpha

BetaAlpha

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Questions…Longman FND page 234-235. Questions 1-6 & Summary

Homework…

Worksheet L15.1

1. How can concrete protect people from gamma radiation?

2. What types of radiation are stopped by a thin sheet of aluminium?

3. Polonium-210 is very radioactive, it emits alpha particles and glows blue. Explain why is safe to store 210Po in a paper bag. (http://en.wikipedia.org/wiki/Polonium)

4. What is background radiation?5. Why is an alpha particle sometimes

referred to as a helium nucleus?6. Alpha and beta radiation can be deflected

by a magnetic or electric field. Gamma radiation cannot be deflected by electric or magnetic fields – explain why.

7. If alpha radiation was deflected upwards by a magnetic field, what way would beta be deflected. Explain your answer

Lesson 4Lesson 4Directing Directing RadiationRadiation

RecapRecap• What are the three types of

radiation?• Match the radiation with its

properties...

• Where does radiation come from?

• Name some sources of radiation?

• Why do we [in Plymouth] get more radiation than people in other parts of the country?

• Describe the process that makes beta radiation.

Alpha An energy beam

Beta Two protons and two neutrons

Gamma

A fast moving electron

Radiation can Radiation can be deflected be deflected

by a by a magnetic magnetic

fieldfield

Properties of alpha, beta and gamma radiation…

Name of radiation

Symbol Passes through:

Is absorbed by:

Alpha α 5cm air only A few cm of air

Beta β Air & paper A thin sheet of paper

Gamma γ Most things except thick lead and concrete

A thick sheet of lead

A very thick wall of concrete

Things to do...Things to do...

• Complete the handout with the properties of alpha, beta and gamma radiation

• Use Longman FND book2, Btec Science book or the AQA book to help

5 / 65 / 6

Aluminium RollersAluminium Rollers

Match the radiation

Alpha

Beta

GammaHelium nuclei

High energy electron

Electromagnetic radiation

Stopped by paper or skin

Reduced by lead

Stopped by aluminium

Background radiation

Background radiation is the radiation all around us. Working in pairs try to think of five possible sources of background radiation.

You have FIVE minutes!!

Rocks Air

Building materials

Outer space

Food

Thin mica Thin aluminiumstops BETA

Thick leadreduces GAMMA

Skin or paper stops ALPHA

The penetration power of the three types of radiation.

Using your results from the previous three investigations, fill in the table below:

Alpha Beta Gamma

Penetrating power

Range of radiation

Most dangerous outside of body

Most dangerous inside of body

Affected by a magnetic field

least medium most

shortest medium longest

least medium most

most medium least

yes yes no

Hydraulicram

detector

Thickness Control Mill

Electronic instructions to adjust rollers.

Beta Source

A radioactive source is on one side of the material and a detector on the other.

If too much radioactivity is getting through, then the material is too thin and the rollers open up a bit to make the material thicker.

If not enough radioactivity is detected then the rollers compress to make the material thinner.

This method is used in the manufacture of lots of sheet materials: plastics, paper, sheet steel.

Assessment – Aluminium Assessment – Aluminium RollersRollers

Scenario:

You need to write a sales pitch trying to sell a new Aluminium rolling machine and sensor to an Aluminium Factory

e.g.

http://www.mettradeindia.com/index.php

Assessment... (P2)Assessment... (P2)AQA Lng 2 Btec What you must do to Pass this assignment...

378 (240) Explain how a Aluminium Roller works (AQA page 378 may help)

234 Work out which would be the most appropriate radiation to use to work out the thickness of the Aluminium (explain what alpha, beta and gamma are, which you would choose and why)

374,

383

234 42 Write down everything you have found out from the theory about alpha, beta and gamma. (What they are, their range, their levels of ionisation, what you need to stop them etc.)

234 Find out what the maximum thickness of Aluminium you could produce and measure by this method you could use

234 Find out what radioactive source you would use for (a) Paper, (b) thick card, (c) lead

234 You must describe the properties of the radiation and why it is stopped by the materials above