Radioactive Emissions 70-71

Question 1

What is the symbol, constituent, relative charge and mass(u) for the radiation alpha.

Answer 1

Symbol : alpha

Constituent : A helium nucleus - 2 protons and 2 neutrons.

Relative charge: +2

Mass(u) : 4

Question 2

What is the symbol, constituent, relative charge and mass(u) for the radiation Beta-minus?

Answer 2

Symbol: ß or ß^-

Consituent: Electron

Relative Charge: -1

Mass(u) : (negligeable)

Question 3

What is the symbol, consituent, reltive charge and mass(u) of the radiation Beta-plus?

Answer 3

Symbol: ß⁺

Constituent: Positron

Relative charge: +1

Mass(u) : (negligeable)

Question 4

What is the symbol, constituent, relative charge and mass(u) for the gamma radiation?

Answer 4

Symbol: gamma

Constituent: Short-wave, high-frequency electromagnetic wave.

Relative charge: 0

Mass(u) 0

Question 5

Why are radioactive emissions also known as ionising radiation?

Answer 5

When a radioactive particle hits an atom it can knock off electrons, creating an ion.

Question 6

For the radiation alpha, how strong is the ionising radiation. What is the speed of the radiation. What is the penetrating power and is it affected by magnetic fields?

Answer 6

Ionising: Strongly

speed: Slow

Penetrating power: Absorbed by paper or a few cm of air.

Affected by magnetic field: Yes

Question 7

How strong is the ionising radiation of Beta minus. What is the speed of the radiation? What is the penetrating power of Beta-minus? Is it affected by magnetic fields?

Answer 7

Ionising: Weakly

Speed: Fast

Penetrating power: Absorbed by 3mm of aluminium

Affected by magnetic field: Yes

Question 8

Why does the Beta-plus not travel very far and not affect many things?

Answer 8

It is annihilated by an electron - so virtually zero range.

Question 9

How ionising is Gamma radiation, what is its speed and what is its penetrating power. And is it affected by a magnetic field?

Answer 9

Ionising: Very weakly

Speed: Speed of light

Penetrating Power: Absorbed by many cm of lead, or several m of concrete.

Not affected by a magnetic field.

Question 10

How does the intensity of gamma radion decrease with distance when travelling through an absorbing material.

Answer 10

Its intensity decreases exponentially.

Question 11

How can the absorbed does be calculated?

Answer 11

absorbed dose = energy/mass

Absorbed dose is measured in grays (Gy)

Question 12

What is the effective dose?

What are its units

How is it calculated?

Answer 12

The effective dose is a measure that lets you compare the amount of damage to body tissues that have been exposed to different types of radiation.

Effective dose = absorbed dose x radiation quality

The unit of effective dose is the siervert ( v)

Question 13

What is the typical radiation quality factor of alpha, beta and gamma?

Answer 13

Alpha: 20

Beta: 1

Gamma: 1

Question 14

If you exposed a sample of body tissue to 1 Gy of alpha radiation, how much gamma radiation would be required to do the same amount of damage.

Answer 14

If you exposed a sample of body tissue to 1Gy of alpha radiation, it could do the same damage as an exposure of 20Gy of gamma radiation on the body tissue.

Question 15

Why is the radiation quality factor for alpha particles really high?

Answer 15

Alpha particles are strongly positive so they can easily pull electrons off atoms, ionising them.

The alpha particle quickly ionises many atoms and loses all it’s energy.

Question 16

Why does beta-minus particle have a lower radiation quality factor?

Answer 16

The beta-minus particle has lower mass and charge than the alpha particle, but a higher speed. This means it can still knock electrons off atoms. Each beta particle will ionise about 100 atoms, loosing energy at each interaction.

This lower number of interactions means that beta radiation causes much less damage to body tissue than alpha radiation - explaining the lower radiation quality factor.

Question 17

Explain some uses of radioactive materials.

Answer 17

They are used to generate power, in medecine for diagnosis and treatment, and to kill harmful microorganisms that might contaminate our food.

Question 18

What harmful problems can radioactive materials cause?

Answer 18

Cancerous tumours, skin burns, radiation sickness, hair loss and even death.

Question 19

What are the two things considered when looking at the risk of using radioactive materials?

Answer 19

How likely it is that the radiation will cause a problem and how bad the problem would be if it did happen.

Question 20

Give two examples of uses of radioactive materials where the risks outweigh the benefits.

Answer 20

1) A nuclear reactor melting down would be catastrophic,but it’s also very unlikely, so the risk might be acceptable.
2) Ionising radiation can cause cancer, but it can also be used in cancer treatments to destroy tumours. The risk of serious damage caused by the treatment is considered acceptable if the treatment is likely to prolong or improve a patient’s life.