Radioactivity and Particles - Radioactivity

Question 1

what are atoms made up of?

Answer 1

protons, neutrons and electrons - protons and neutrons are in the nucleus, electrons are in the shells

Question 2

what is atomic number?

Answer 2

the number of protons in the nucleus of an atom

Question 3

what is mass number?

Answer 3

the total number of protons and neutrons in the nucleus of an atom

Question 4

what is an isotope?

Answer 4

an atom of the same element, but has a different number of neutrons/different mass number

Question 5

what are the 3 types of ionising radiation?

Answer 5

Alpha (α), Beta (β) and Gamma (γ)

Question 6

what is ionisation?

Answer 6

when an atom loses or gains an electron, causing it to become an ion (an atom which is positively or negatively charged)

Question 7

what is the ionising power and range in air of alpha particles?

Answer 7

• strong ionising power
• a few cm range
• stopped by paper

Question 8

what is the ionising power and range in air of beta particles?

Answer 8

• moderate ionising power
• 1m range
• stopped by aluminium

Question 9

what is the ionising power and range in air of gamma particles?

Answer 9

• very weak ionising power
• atleast 1km range
• stopped by lead

Question 10

how would you investigate the penetration powers of different types of radiation?

Answer 10

• detect using a Geiger Müller Tube
• first note the measurement without any sources (CMBR)
• try the three different materials in order: paper, aluminium then lead.
• the count rate will significantly decrease if radiation is stopped

Question 11

what are the effects of alpha decay on the atomic and mass numbers of a nucleus?

Answer 11

• 2 protons and 2 neutrons are lost
• mass number decreases by 4
• atomic number decreases by 2

Question 12

what are the effects of beta decay on the atomic and mass numbers of a nucleus?

Answer 12

• 1 neutron is converted to an electron (lost from the atom) and proton
• mass number is unchanged
• atomic number increases by 1

Question 13

what are the effects of gamma decay on the atomic and mass numbers of a nucleus?

Answer 13

• energy is lost from an atom in the form of an electromagnetic wave
• mass number is unchanged
• atomic number is unchanged

Question 14

what can detect ionising radiations?

Answer 14

photographic film or a Geiger−Müller detector
- when connected to a counter, the detector will be able to measure radioactivity
- radiation will cause photographic film to darken

Question 15

what are the sources of background radiation?

Answer 15

• radon in the air
• granite in rocks
• cosmic rays
• medical equipment
• food and drink

Question 16

what happens to the activity of a radioactive source over time?

Answer 16

the activity of a radioactive source decreases over a period of time

Question 17

what is the activity of a radioactive source measured in?

Answer 17

becquerels

Question 18

what is half-life?

Answer 18

the half-life is the time taken for the radioactivity of a specific isotope to fall to half its original value

Question 19

how is gamma used as a medical tracer?

Answer 19

• radioactive tracer put in body (swallowed/injected)
• detector put around body
• computer generates an image

Question 20

how is gamma used in radiotherapy?

Answer 20

• high doses of radiation are directed at cancer cells
• cancer cells are killed

Question 21

how is gamma used as a pipe tracer?

Answer 21

• a radioactive material which emits gamma radiation with a short half-life is put in the water
• a detector is placed above the pipe
• a spike in detected radioactivity suggests a leak in the pipe

Question 22

how is gamma used in sterilisation?

Answer 22

• medical equipment irradiated
• kills all living matter on tools (e.g. bacteria)

Question 23

what is contamination?

Answer 23

contamination occurs when material that contains radioactive atoms is deposited on materials

Question 24

what is irradiation?

Answer 24

the process by which an object is exposed to radiation

Question 25

what are the dangers of ionising radiation?

Answer 25

• can cause cell mutation/death
• can damage tissue
• hard to dispose of (needs to be in a secure area and in multiple lead-lined boxes)

Question 26

how can you reduce the risk of ionising radiation?

Answer 26

• keep sources away from the body
• wear gloves when handling
• minimise time spent in areas with high radiation