P4

Question 1

What is activity?

Answer 1

The rate at which a source of unstable nuclei decays
Measured in becquerel(Bq)

Question 2

What is count-rate?

Answer 2

Count-rate is the number of decays recorded each second by a detector

Question 3

What can be used to measure the count-rate?

Answer 3

A Geiger-Muller tube

Question 4

What is half-life?

Answer 4

The amount of time it takes the number of nuclei of the isotope in the sample to halve

Question 5

What are the three types of radiation?

Answer 5

•alpha
•beta
•gamma

Question 6

What is an additional cause of radiation?

Answer 6

neutrons

Question 7

Properties of alpha radiation

Answer 7

• consists of two neutrons, two protons (like helium)
• overall +2 charge
• does not penetrate far into materials(can be absorbed by a single sheet of paper)
• highly ionising
• has a range of a few cm in the air
• deflects towards the negative pole of an electric field
• uses; smoke tracers

Question 8

Properties of beta radiation

Answer 8

• consists of a high speed electron
• has a -1 charge
• moderately ionising
• range of a few m in the air
• penetrates moderately far into material (further than alpha), can be absorbed by a thin sheet of metal(aluminium)
• uses; medical tracing

Question 9

Properties of gamma rays

Answer 9

• part of the EM spectrum
• typically after alpha or beta radiation to transfer energy
• waves that penetrate far into materials, can be absorbed by concrete or thick sheets of lead
• weakly ionising
• uses; radiotherapy, medical tracers

Question 10

Define irradiation

Answer 10

the process by which an object is exposed to radiation

Question 11

Define contamination

Answer 11

the unwanted presence of a material containing radioactive atoms on other materials

Question 12

Give natural sources of background radiation

Answer 12

• cosmic rays
• rocks
• radon gas

Question 13

Give man made sources of background radiation

Answer 13

• nuclear weapon testing
• nuclear accidents

Question 14

What may levels of radiation be affected by?

Answer 14

• location
• occupation

Question 15

What determines how harmful radiation is?

Answer 15

• type of radiation e.g. ionising-cause mutations in cells

where you’re exposed to it: outside=most harmful → beta/gamma
on/inside the body= most harmful → alpha

the amount(dosage):
• distance from the source
• how long you’re exposed for
• how radioactive the substance is

Question 16

Explain uses of radiation in medicine

Answer 16

radiotherapy: can be used to kill off cancer cells, can be external(gamma rays) or internal(beta source inside the body)
• can cause radiation sickness
• damages other healthy cells

medical tracers: can be used for detection as the movement of isotopes is tracked around the body, can check if particular organs work properly depending on how much the organ absorbs
•typically gamma, but beta can also be used

Question 17

Why would you use an isotope with a short half-life?

Answer 17

only emit radiation for a short period and then stop being harmful

Question 18

What is nuclear fusion?

Answer 18

a nuclear reaction in which atomic nuclei of low atomic number fuse to form a heavier nucleus with the release of energy

Question 19

Where does nuclear fusion happen? why?

Answer 19

in stars because it required extremely high temperature(hence high levels of energy)

Question 20

What is nuclear fission?

Answer 20

the splitting of an unstable nucleus to two smaller nuclei

Question 21

Where does nuclear fission happen?

Answer 21

In nuclear power stations

Question 22

Why is nuclear fission a chain reaction?

Answer 22

it releases other neutrons and energy(in the form of gamma rays) which means these neutrons can be absorbed by another nucleus and this would cause the nucleus to spilt into smaller nuclei