Radioactivity

Notes on the different types of radioactivity (alpha, beta & gamma) and their uses in industry.

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  • Created by: Hollie
  • Created on: 23-06-11 16:47

Nuclear Radiation

Atoms always contain:

  • Protons (+)
  • Neutrons (+-)
  • Electrons (-)

Atoms always have the same number of protons however isotopes have different numbers of neutrons

A radioactive substance always contains an unstable nuclei - they emit radiation and turn into other elements

Radioactive decay is a random process - it is not effected by external conditions

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Alpha Radiation

Alpha is a helium nucleus made up of 2 protons and 2 neutrons

The particles are quite large which results in lots of collisions - this means they cannot penetrate far into a material

Stopped by:

  • Human skin
  • Paper
  • Few centimetres of air

Aplha particles are most dangerous if they are in the body - they are strongly ionising

Because of their positive charge they are deflected by electric and magnetic fields

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Beta Radiation

A beta particle is a high speed electron found in the nucleus.

The particles are a lot smaller than alpha particles resulting in less collisions - this makes them less ionising and more penetrating

Stopped by:

  • Thin sheet of aluminium
  • Few metres of air

Beta particles have a negative charge

They are deflected by electric and magnetic fields oppositely to alpha particles

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Gamma Radiation

Gamma radiation has a very short wavelength and is emitted from the nucleus.

As gamma rays are electromagnetic waves, they will travel a long time before colliding with an atom - not very ionising and very penetrating.

Stopped by:

  • Thick piece of lead ( few centimetres)
  • Several metres of concrete
  • Unlimited range of air

Gamma rays are not deflected by electric or magnetic fields.

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Effects of Radiation on the Body

The danger of a radiaactive substance on the body depends on whether the radiation is in or outside of the body.

Inside the Body

  • Alpha is most dangerous - it is easily absorbed by the cells
  • Beta & Gamma aren't very dangerous - they are unlikely to be absorbed and would usually pass straight through the cells

Outside the Body

  • Alpha isn't very dangerous - it is unlikely to reach cells inside the body
  • Beta & Gamma are most dangerous - both are very penetrating so can penetrate the skin and damage the inside of cells.
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Using Radiation in Industry

Radiation plays a big part in industry - depending upon its half life and the type of radiation it gives outs.

Examples include:

  • Smoke detectors (alpha)
  • Mearugin the thickness of materials, e.g. paper (beta)
  • Tracers for medical diagnosis (gamma/beta)
  • Sterilising medical treatment (gamma)
  • Killing cancer cells (gamma)

The half life of these radiations are very important. For example, medical tracers need a half life of only a few hours so that the radiation is not exposed to the body for too long.

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Half- Life

The radioactivity of a material decreases gradually over time till it falls to nearly zero.

The idea of half life is used to measure how quickly this radioactivity decreases.

Definitions for half life:

The time in which it takes for the count rate of a substance to fall to half its initial value

The time it takes for the number of nuclei in an isotope to halve.

Example - a substance drops from 20 counts per minute to 10 counts in 15 days. The half life therefore is 15 days.

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Comments

Olaf

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:)

Miss KHP

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A wonderful set of revision cards of radioactivity. They can be used for all exam boards as they are a nice and simple and will help you understand it. You may decide to add them to your own revision cards and so this will save you time.

Dhylan2001

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Very useful :)

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