radiation

Question 1

what is the name of equipment used to measure ionising radiation?

Answer 1

geige muller tube

Question 2

What precautions should be taken when using radioactive sources?

Answer 2

• minimise time handling the source
• use a lead apron/shield
  -take care to direct emissions of source away from people
  -store source in a lead box(when not in use)
• maximise the distance to the source
• handle the source with tongues
  store the source in a lead-lined box

Question 3

Describe how you can use a Geiger Muller tube to compare a corrected count rate of different sources.

Answer 3

• corrected count rate = count rate - background count
• you can find the background count by having no source present, then measure the reading on the geiger muller tube
• place one of the sources infront of theGM tube.
• record the count
  -Make sure you count the background and source count for the same amount of time or ur result will be inaccurate
  -repeat for 2 other sources
  -repeat the readings and find a mean

Question 4

What is meant by the random nature of the radioactive decay?

Answer 4

• it is impossible to tell WHICH nuclei will decay next
• impossible to tell WHEN the nuclei will decay

Question 5

What is half life?

Answer 5

• time taken for the activity of the radioactive sample/isotope/nuclide to half.
  OR
  –time taken for the number of radioactive nuclei in the sample to half

Question 6

What is equation to calculate hoow much particles left in a sample after an amount of time?

Answer 6

initial amount / 2^amount of time/half life

Question 7

How do you find the age of an artefact?

Answer 7

age = number of half lives x half life

Question 8

Why is it impossible to age fossils using carbon dating?

Answer 8

• it is impossible to distinguish between background radiation and the activity of the fossil
  -the activtiy from the fossil would be very small and difficult to detect.
• as materials fossilise, the carbon is replaced with minerals, so there would be no carbon to decay.

Question 9

what is gamma radiation?

Answer 9

high energy electromagnetic wave

Question 10

How do you use a geiger muller tube to know which type of radiation is which (with paper, 5mm allumiinium and lead)

Answer 10

• record the count rate wiiithout the absorbing material
• repeat with an absorbing material between the source and the geiger muller tube
• if the radiation is able to penetrate through the material the count rate will stay the same(or reduce slightly)
  -if the radation is absorbed by the material, the count rate recorded will fall to background radiation level.

Question 13

Why is it dangerous to ingest alpha radiation?

Answer 13

• alpha is highly ionising
  so:
  -increased risk of cancer
  -radiation sickness
  -mutation of genes
  -damage to cells/tissue/organs

Question 14

When radiation is stopped, where does it actually go?

Answer 14

it is absorbed by that material

Question 15

Why is it safe to eat fruit that has been irradiated with gamma rays?

Answer 15

• gamma rays kill microorganisms on the druit
  -gamma is not in contact with fruit when being eaten
• fruit is not contaminated after it has been irradiated

Question 16

describe how radioactive tracers are used in medical imaging

Answer 16

radiactive tracer is injected/ingested
then radiation emitted by the tracer is detecting, creating an image of the area being examined

Question 17

Describe how radioactive substances are used in smoke detectors.

Answer 17

alpha particles ionise the air creating a current
this current is interrupted when smoke enters the detector whicih triggers the alarm

Question 18

what are precautions and safety measres taken to minismise the risks associated with emiitting sources in smoke detectors.

Answer 18

-alpha has a low penetratiing capability so wont be able to leave the smoke detector
-it has a very low range in air
- alpha source is enclosed, preventing direct exposure to alpha radiation.
-the amount of radioactive material used in smoke detectors.

Question 19

What are the advantages and safety precautions of using radiactive tracers for leak detection in pipelines (4)

Answer 19

advantage:
- has the ability to detect leaks in inaccessible or underground pipes
- it has a high sensitivity for leak detection

safety precautions:
- must use a radiactive isotope with a suitabe half life to prevent unnecessary lonng term radiation levels
- radiactive sources must be stored in suitable containers such as lead lined boxed
- radiactive sources must be handles with care

Question 20

what is meant by background radiation

Answer 20

low level radiation that is present in the environment at all times

Question 21

name 4 sources of background radiation

Answer 21

• cosmic rays
• natural radioactive materials in the earth
• human-made sources like medical tracers
• some foods(bananas)

Question 22

why is an unstable sample of radioactive nuclei of radium with a moderate half life of about 12 days that emits alpha radiation suitable for us einside the body to treat cnacers.

Answer 22

-alpha is highly ionising
-alpha kills cancer cells
-alpha does not peentrate very far in the body so it wwiill stay close to the injection site
- its half life is long enough for the tratment to take effect
- the half life is short enough that it wont last very long in the body and will not be needed to be removed.

Question 23

Why is alpha not used for medical tracing

Answer 23

• alpha is highly ionising
  – alpha can kill healthy cells
• alpha does would not be detected outside the body as it has a low peentrating ability