Radiation

Question 1

What happens during ionising radiation?

Answer 1

Alpha, beta and gamma particles are emitted from an unstable nuclei (which has now decayed) and collide with atoms, causing them to lose electrons

Question 2

What are the charges and masses of alpha, beta and gamma?

Answer 2

Alpha has a mass of 4 and a charge of +2
Beta has mass of 1/1840 and a charge of -1
Gamma has no mass or charge

Question 3

What are the properties of gamma rays?

Answer 3

Very penetrating (need thick led to stop them)
Weakly ionising
Can travel a few km in air

Question 4

What are the properties alpha particles

Answer 4

Not very penetrating
Very ionising
Will travel a few cm in air

Question 5

What is the activity (Bq) of a radioactive source?

Answer 5

The number of atoms that decay each second

Question 6

What is the half-life of a radioactive source?

Answer 6

The time it takes for half of the unstable atoms to decay

Question 7

Ionising radiation turns atoms into ions. Why is this dangerous? What safety precautions should be taken?

Answer 7

Because ions can cause mutations to the DNA in cells, which can lead to cancers and tumours.
Limit time of exposure and wear protective clothing (lead apron will absorb radiation)

Question 8

Define irradiation and state the effects

Answer 8

Ionising radiation from an external source (eg. X-rays).

Cells may become damaged or killed, but you won’t become radioactive

Question 9

Define contamination

Answer 9

When a radioactive source comes into contact with the body (external) or is consumed (internal)

Question 10

What happens during nuclear fission?

Answer 10

A large unstable nuclei splits up into two daughter nuclei when it absorbs a neutron. It releases 2 or more neutrons and some energy.

Question 11

How does a chain reaction take place and why is it dangerous?

Answer 11

If the neutron that is released is absorbed by another nuclei this causes a chain reaction. If it is not controlled, there will be a nuclear explosion

Question 12

How do nuclear reactors control chain reaction?

Answer 12

The control rods absorb neutrons and the moderators slow the neutrons down. If the control rods are pushed further into the core, more neutrons are absorbed and the reaction slows down

Question 13

What is nuclear fusion?

Answer 13

When two smaller nuclei join together to form a larger one (hydrogen nuclei fuse to form helium nuclei)

Question 14

Why is nuclear fusion difficult to produce in power stations?

Answer 14

Because the nuclei need to get very close together to overcome the electrostatic repulsion. This requires very high pressure and temperature

Question 15

What is the main source of background radiation

Answer 15

Radon gas - formed when uranium in rocks decay - emits alpha particles

Question 16

What does a Geiger-Muller tube do and how does it work?

Answer 16

It detects radiation.
The GM tube contains argon gas, so when the radiation enters it ionises the argon atoms, and electrons travel through a thin wire connected to a voltage. The amount of radiation detected is shown by the rate meter

Question 17

Describe the plum pudding model of an atom

Answer 17

Electrons are embedded in a positively charged ‘dough’ - showed that both positive and negative charges existed and accounted for the atom being neutral
(Rutherford’s is modern day)

Question 18

How do smoke alarms work?

Answer 18

They contain alpha particles, which ionise air and form a current. When smoke enters the smoke alarm, it absorbs the alpha particles, causing their current to fall. A detector senses this fall and a siren sounds

Question 19

What are beta and gamma particles used for?

Answer 19

Beta controls the thickness of paper

Gamma can be used to sterilise objects, kill cancer cells, etc

Question 20

What are the advantages and disadvantages of using nuclear power to generate electricity?

Answer 20

Adv: doesn’t produce CO2, supplies will last longer than fossil fuels
Dis: produces radioactive nuclear waste-difficult and expensive to store. Can be dangerous - risk of nuclear accidents