general

Question 1

what must gamma radiation be blocked by

Answer 1

thick lead or concrete

Question 2

what can beta be blocked by

Answer 2

thin sheet of aluminium

Question 3

what can alpha be blocked by

Answer 3

• paper
• few cm of air
• skin

Question 4

order the radiation from strongest to weakest penetration

Answer 4

• gamma
• beta
• alpha

Question 5

order the radiaton from strongest to weakest ionisation

Answer 5

• alpha
• beta
• gamma

Question 6

irradiation is

Answer 6

when an object absorbs radiation from a source

Question 7

contamination is

Answer 7

when a radioactive source is on or in a person or object

Question 8

why can both irradiation and contamination be harmful

Answer 8

both can lead to mutation of DNA

Question 9

why might an object being irradiated not be dangerous after a period of time

Answer 9

• radiation absorbed given back off to surroundings
• until same background levels of radiation

Question 10

why is contamination by alpha radiation inside the human body dangerous

Answer 10

• alpha radiation is highly ionising
• may lead to mutation of DNA or radiation sickness
• radioactive source must be removed from person or wait until all has decayed back to background radiation

Question 11

equation used with half life

Answer 11

• new activity = initial count rate or activity / 2^n
• where n = no. of half lives

Question 12

A teacher used a Geiger-Muller tube and counter to measure the number of counts in 60 seconds for a radioactive rock.

The counter recorded 819 counts in 60 seconds.

The background radiation count rate was 0.30 counts per second.

Calculate the count rate for the rock in counts per second.

Answer 12