P2 - Atoms and Radiation

Question 1

What emits radiation?

Answer 1

Isotopes with an unstable nucleus emit radiation or decay.

Question 2

What are the three forms of radiation?

Answer 2

Alpha Particles Beta Particles Gamma Rays

Question 3

Why is radioactivity random?

Answer 3

It is random when you look at a small number of atoms but when you look at a large number of atoms there is a pattern.

Question 4

What is half life?

Answer 4

Half life is the time it takes for a radioactive source to lose half of it’s initial nuclei or initial activity.

Question 5

Sample X has a count rate of 1024. It has a half life of 2 days? What is the count rate after 6 days?

Answer 5

1024 > 512 > 256 > 128 2 2 2

Question 6

What is the most dangerous radiation to humans?

Answer 6

Alpha radiation is the most dangerous for humans because it is the most likely to be absorbed by the cells and it is the most ionising whereas beta or gamma would pass straight through. However, it is easy to protect from alpha because it is absorbed by a few cm of air or a few sheets of paper. It is harder to protect from beta and gamma.

Question 7

What happens when ionising radiation hits your cells?

Answer 7

When the ionising radiation hits your cells it causes atoms in your body to become ionised, gaining or losing electrons. This causes mutations and cancer.

Question 8

How can we measure how much radiation is given off?

Answer 8

Using a geiger counter. This measures the count rate of radiation emitted. Higher count rate = more radiation given off.

Question 9

What is an alpha particle?

Answer 9

Alpha particles are made from 2 protons and 2 neutrons. They carry a +2 charge. It is a helium nucleus. 4 a 2 They are highly ionising.

Question 10

What is a beta particle?

Answer 10

A beta particle is a fast moving electron which has a -1 charge. It is moderately ionising.

Question 11

What is a gamma ray?

Answer 11

A wave. It is weakly ionising.

Question 12

What absorbs alpha particles?

Answer 12

Paper

Question 13

What absorbs beta particles?

Answer 13

Aluminium

Question 14

What absorbs gamma rays?

Answer 14

Lead.

Question 15

What is the alpha decay equation?

Answer 15

Take 2 from the bottom number and 4 from the top number, eg. 240 236 4 Pu -> U + a 94 92 2

Question 16

What is the beta decay equation?

Answer 16

A neutron changes into a proton and an electron. 14 14 C -> C + e 6 7 -1 Add one to the bottom number. Add -1 e on the end.

Question 17

Explain this.

Answer 17

Beta is a fast moving electron with a negative charge so it is attracted to the positive side.

Alpha has a +2 charge so is attracted to the negative side.

Gamma continues as it has no charge.

Beta curves more than alpha because it has a negligible mass, less than alpha, so less force is required to change direction.

Question 18

What is background radiation?

Answer 18

Radiation which has been measured when there has been no source of radiation.

Question 19

List 3 man made sources of background radiation.

Answer 19

1) Nuclear Weapons
2) Nuclear Power
3) Medical (eg. X Rays, Radiotherapy)

Question 20

List 3 natural sources of background radiation.

Answer 20

1) Cosmic Rays
2) Food and drink
3) Radioactive rocks (eg. granite giving off argon) such as in Cornwall.

Question 21

How can alpha particles be used?

Answer 21

Alpha particles can be used in smoke alarms.

There is a alpha source inside the smoke alarm giving off alpha particles. These particles ionise the air allowing the circuit to be completed.

If there is smoke it absorbs the alpha particles so they do not get in the gap. The circuit is broken which triggers the smoke alarm.

Question 22

How can beta be used?

Answer 22

Beta can be used to control the thickness of a material.

Beta particles are fired through the metal. A gieger counter detects the number of particles getting through.

If the radiation is too high then the metal is too thin, the rollers can then make the metal thicker.

If the radiation is too low then the metal is too thick. The rollers can make the metal thinner.

Beta is used because alpha would be absorbed by the metal and alpha particles would go straight through.

Question 23

How can beta or gamma be used in medicine?

Answer 23

Beta and Gamma can be injected as tracers. A radioactive isotope with a short half life is used so that you do not harm other people around you but it can’t be too short that it won’t be detected.

Question 24

How can gamma be used?

Answer 24

Gamma can be used to find the leak in pipes.

Gamma rays are fired along a pipe where there is known to be a crack.

A machine such as a gieger counter is sent out above the pipes and detects the gamma radiation.

Readings outside the leak will be regular. The ones where the leak is will fluctuate.

You can then dig up the area around the leak and fix it. This saves time and money than digging up the whole pipe.

Gamma can be used over long distances.