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What is radiation?What is radiation?

L/O ;- To know what causes background radiation

Do you have any of these Do you have any of these detectors at home? What detectors at home? What

are they?are they?

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Smoke detector

Radon gas detector

Carbon monoxide detector

21/04/23You have grown up on a planet which has, in places, quite a high level of background radiation, and life on Earth has evolved to cope with this. Your cells have self-repairing mechanisms which allow them to survive relatively unscathed.

What do you think may be different

about the areas in red to give them

higher background radiation?

•The amount of background radiation varies considerably around Britain, as shown on the map. You can see that it is particularly high in Cornwall, because of the types of rock there

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Background RadiationBackground Radiation

Radon gas

Food

Cosmic rays

Gamma rays

Medical

Nuclear power

13% are man-made

21/04/23Introduction to Introduction to RadioactivityRadioactivity

Some substances are classed as “radioactive” – this means that they are unstable and continuously give out radiation:

Radiation

The nucleus is more stable after emitting some radiation – this is called “radioactice decay”.

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When isotopes decay they often give out When isotopes decay they often give out Alpha, Beta or Gamma radiationAlpha, Beta or Gamma radiation

21/04/23Types of Types of radiationradiation

Unstable nucleus

Unstable nucleus

Unstable nucleus

New nucleus

New nucleus

New nucleus

Alpha particle

Beta particle

Gamma radiation

Alpha Radiation ()

An alpha particle contains 2 protons and 2 neutrons (a Helium nucleus). Because the atom has lost protons, it becomes a different element (mass decreases by 4)

Beta Radiation ()

A Beta () particle is a high energy electron from the nucleus. When this is released, a neutron changes into a proton. This means a new atom is formed

Gamma Radiation ()

After or decay, excess energy is sometimes given off. This is called Gamma radiation (wave with a high frequency and short wavelength). Because the proton number does not change, the atom remains the same

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Blocking RadiationBlocking RadiationEach type of radiation can be blocked by different materials:

Sheet of paper

Few mm of aluminium

Few cm of lead

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Assessed Question Assessed Question

Why do you think alpha radiation is the least

penetrating?

Which do you think is the most dangerous outside your body?

Why?

Which do you think is the most dangerous

inside your body? Why?

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Dangers of radioactivityDangers of radioactivity

OUTSIDE the body and are more dangerous as radiation is blocked by the skin.

INSIDE the body an source causes the most damage because it is the most ionising.

Alpha

Beta

Radiation will ionise atoms in living cells – this can damage them and cause cancer or leukaemia.

Gamma

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Different types of electromagnetic radiation are used for different jobs

Choose words from the list to complete the table

Gamma rays / light / microwaves / radio waves / ultraviolet

TYPE OF RADIATION WHAT THE RADIATION IS USED FOR

to send along optical fibres in an endoscope

to give skin a tan (but can cause cancer in cells)

to sterilise surgical instruments

to send information to and from satellites

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g am m ara ys A

ultra v io le tray s lig h t B m icro

w av esra d io

w av e s

S h o rtes t w a v e len g th L o n g es t w av e le n g th

Complete the following.

A = ................................................. B = ................................................

(c) Our bodies are exposed to gamma radiation all the time. Write down two sources of this gamma radiation.1 .................................................... 2 .................................................

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wrappedin paper

wrapped inaluminium foil

reading almostas high

much lowerreading

high reading

A piece of rock gives a high reading with a radiation detector.

The diagrams show what happens when rock is wrapped in paper and

aluminium foil What type of radiation does the rock emit?

Explain your answer

You can use the rock to measure the thickness of different types of aluminium foil

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A

B

C

R ad ioa c tiv esu b sta n ces

th in p ap er th in m e ta l th ick le ad

= s tro n g ra d ia tio n

= w ea k ra d ia tio n

RADIOACTIVE SUBSTANCE

TYPE OF RADIATION IT EMITS

A

B

C

The diagram shows what happens to the radiation from 3 radioactive substances when different materials are put in their way

Fill in the table from

Alpha / Beta / Gamma / UV

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(a) Radiation can cause cancer. The graph shows that the risk of cancer depends on the radiation dose a person is exposed to.

H ig h

L o w

K n o w n e ffec t

P ro b ab le e ffec t

R ad ia tio n d o seL o w H ig h

R isk o fcan ce r

Complete the following sentence.The ................................................ the dose of radiation a person gets, the greater the risk of cancer.

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5. (a) There are three types of radiation, alpha, beta and gamma.

The diagram shows what can stop the radiation from two different sources.

A m eric iu m

S tro n tiu m

T h inca rd b o a rd

6 m malu m in iu m

Which type of radiation, alpha, beta or gamma is given out by:

(i) Americium

(ii) strontium?

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Diagram 1 shows the position of a smoke detector inside a house. Diagram 2 shows the warning label at the back of the smoke detector.

Explain why the radiation given out by the americium is unlikely to do any harm to people living in the house.

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(c) The graph shows how the number of americium atoms inside a source goes down slowly.

1 0 0 0 0

9 0 0 0

8 0 0 0

7 0 0 0

6 0 0 0

5 0 0 0

4 0 0 0

3 0 0 0

2 0 0 0

1 0 0 0

0

0 1 0 0 2 0 0 3 0 0 4 0 0 5 0 0 6 0 0 7 0 0 8 0 0 9 0 0 1 0 0 0

N u m b er o fam eric iu m

a to m s

Tim e in y ea rs

The battery inside the smoke detector lasts one year and is then replaced. Explain why the americium source will never need to be replaced.