Ch7 Radioactivity

Question 1

radioactive decay

Answer 1

unstable nuclei gives out radiation as it changes element to become more stable

Question 2

Geiger-Muller tube

Answer 2

records the number of decays recorded each second(count-rate or activity)

Question 3

alpha

Answer 3

4 He

2

Question 4

beta

Answer 4

0 e
-1

high speed electron ejected from the nucleus as a neutron turns into a proton

Question 5

gamma ray

Answer 5

electromagnetic radiation from the nucleus of a neutron

Question 6

gamma ray

1. range in air
2. ionising power
3. absorbed by…
4. example of use

Answer 6

1. longer distances
2. weak
3. thick sheets of lead
4. medical tracers

Question 7

alpha particle

1. range in air
2. ionising power
3. absorbed by…
4. example of use

Answer 7

1. few cm
2. strong
3. sheet of paper
4. smoke detector

Question 8

beta particle

1. range in air
2. ionising power
3. absorbed by…
4. example of use

Answer 8

1. few metres
2. moderate
3. sheet of aluminium
4. material thickness testing

Question 9

half-life

Answer 9

the time it takes for the number of nuclei of the isotope in a sample to halve

for the count rate from the isotope in a sample to halve

Question 10

half-life formula

= number of nuclei left

Answer 10

(1/2)^halflifes x mass(g)

Question 11

radioactive contamination

Answer 11

unwanted presence of materials containing radioactive atoms on other materials
due to decay of the nuclei of the contaminating atoms
type of radiation emitted affects the level of hazard

Question 12

irridation

Answer 12

the process of exposing an object to ionising radiation

irradiated object does not become radioactive

Question 13

precautions against irridation

Answer 13

1. keep sources in lead lined box
2. stand far away from sources
3. handle sources with remote

Question 14

ionising radiation

Answer 14

radiation that knocks electrons off of atoms, creating charged ions

Question 15

smoke alarms

Answer 15

contain a radioactive isotope that sends alpha particles into a gap in the circuit
alpha particles ionise the air so there is a current across the gap
smoke absorbs the alpha particles, preventing them from ionising the air
current drops and makes the alarm sound
beta + gamma can’t be used because they don’t create enough ions to create electricity

Question 16

thickness monitoring in metal foil production

Answer 16

uses a radioactive source that sends out beta radiation
detector measures the amount of radiation that passes through the foil
if foil is too thick, detector reading drops and sends a signal to increases pressure of metal rollers
this makes sheet thinner again

Question 17

activity

Answer 17

number of unstable atoms in the source that decay per second