atoms and nuclear radiation (topic 4) Flashcards
alpha: two protons and two neutrons
beta: electron from the nucleus
gamma: electromagnetic radiation
gamma
beta
alpha
- radioactive source not pointed at students
- radioactive source outside the box for minimum time necessary
- eye protection
- radioactive source held away from body
cout rate = total count/time taken
?
- alpha particles cannot pass through
or - alpha particles can pass through a very thin sheet of paper / card
4500 million years
(2)
- half-life too long
- no measurable change in count rate
- (the detector) reading had gone down
- more beta (particles / radiation) is being absorbed
(in a system used to control the thickness of cardboard as it is
made)
in a system used to control the thickness of cardboard as it is made why would it not work if the beta radiation source was replaced by an alpha radiation source
alpha would not penetrate the cardboard
why is it important to warn people that a radiation source is being used
radiation damages our cells
- M
- less radiation / beta (particles) absorbed
- cannot penetrate aluminium
- gamma rays not affected (by aluminium)
(1) (2)
- (nuclei) unstable
- causes harm / damage to body / cells
- causes mutations / causes cancer
- beta
- alpha absorbed by paper
- or beta is absorbed by aluminium
- or gamma would affect all film
(2)
- two half lives
- 20 minutes
(2)
- alphas will be stopped by skin / air or do not penetrate
- betas and gammas can damage cells
(3)
- have the source and GM tube/detector fixed distances apart
- measure the initial count rate
- place a sheet of paper imbetween, record the count rate
- replace the paper with a sgeet of aluminium, record the count rate
- if the count rate is stopped by paper then the source emits alpha
- if the source is not stopped by paper but is by aluminium then the source emits beta
- (changes to) background radiation
or - (beta) decay is random
what can you say about the thickness of the cardboard being made at 10:30, explain reason for answer (3)
- thickness decreasing
- increased count rate
- (means) less (beta) radiation absorbed
explain why gamma radiation is not suitable for detecting changes to the
thickness of the cardboard (1)
- changing thickness will not change count rate (significantly)
(3)
- alpha: the card absorbs alphas but not betas
- beta: the thin metal absorbs alphas and betas
- gamma: would pass through the thin metal so a higher reading would be recorded
- nuclear reactor
- star
- nuclei are joined (not split)
(4)
- neutron
- absorbed by U nucleus
- forms a larger nucleus
- which is unstable
- larger nucleus splits into two smaller nuclei, Ba and Kr
- releasing three neutrons and energy
(atomic number is 56), would usually be at top but switched for isotopes (protons and neutrons), equals number of electrons
during beta decay, an unstable atomic nucleus emits an electron (so atomic number increases by one) and an antineutrino while converting a neutron to a proton
cars
gamma
describe how the teacher can use a GM tube to compare the corrected count rate of three different sources
- corrected count rate = count rate - background count
- with no source present, record background count
- place one source in front of GM-tube
- record count with source 1
- background count and source count recorded for the same duration
- repeat for other two sources
- repeat readings and calculate averages
explain what is meant by the random nature of radioactive decay (2)
- impossible to tell which nuclei will decay next
- impossible to tell when the nuclei will decay
explain what is meant by the term half-life
time taken for the activity of the radioactive sample to half
explain why it is impossible to age fossils using carbon dating
- as materials fossilise the carbon is replaced with minerals
- so there would be no carbon to decay
describe how the teacher would know if the alpha, beta, or gamma radiation had been absorbed by the materials above (3)
- the teacher will record the count rate without the absorbing material
- repeat with an absorbing material between the source and the GM-tube
- if the radiation is able to penetrate through the material the count rate will stay the same or reduce slightly
- if the radiation is absorbed by the material, the count rate recorded will fall to background radiation level
give two safety precautions the teacher should take when using radioactive sources
- care taken not to point source at people
- minimise time source is out of container
- store source in a lead lined box
- gloves
- source held away from body
- source held with tongs
- alpha particle has an atomic number of 2 and a mass number of 4 because (2 protons and 2 neutrons)
- mass number of radon = 226 - 4 = 222
- atomic number of radon = 88 - 2 = 86
smoke alarms in houses contain a source of alpha radiation, explain why it is safe to have an alpha emitter in a smoke alarm (2)
- alpha has a low penetrating capability
- alpha will be absorbed by the casing of the smoke alarm
- alpha has a range in air of only a few cm
state which isotope has 147 neutrons
C
- correct numbers for beta particle
- nitrogen mass number = 14
- nitrogen atomic number = 7
gamma radiation is used to irradiate fruit, explain why it is safe to eat fruit that has been irradiated with gamma rays
- gamma rays kill microorganisms on the fruit
- gamma is not in contact with fruit when being eaten
- fruit is not contaminated after it has been irradiated
