Studied by 1 personA = λ ⋅ N
Activity = Decay Constant ⋅ (Number of Undecayed Nuclei)
A=A₀e^-λt
(CURRENT activity) = (INITIAL activity) × e ^ -(Decay constant × Time)
Calculate the total charge of a neutron:
0 (no charge)
What is the charge of an up quark?
+2/3 e
d = -1/3
d = -1/3
0 (no charge)
Calculate the total charge of a proton:
u = +2/3 e
u = +2/3 e
d = -1/3 e
e
How can the decay of Rubidium-87 be used to date rocks and meteors?
-Rubidium-87 emits Beta-Minus particles and transform into Strontium-87
How do you calculate the radius of a nucleus ?
Radius = (radius of a proton) x (nucleon number)^1/3
How do you carbon date something that is as old 50,000 years old?
Mass spectrometry
How do you model exponential decay?
Start with a given number of un-decayed nuclei
Choose a very small time interval compared with the half-life
Calculate the number of nuclei decaying by using ΔN/Δt = λN
4.Calculate the number of un-decayed nuclei at the end of the Δt and subtract it from the previous value for N
Repeat steps 4 for multiple subsequent time intervals
How does Carbon Dating work?
As the organism dies, the amount of carbon-14 stops increasing and starts to decay.
The ratio of C-14 : C-12 decreases over time.
The age of the organism can be determined by comparing the ratios of C-14 to C-12 from its death until now.
How is Carbon-14 formed?
High speed protons in cosmic rays collide with atoms in the upper atmosphere to produce neutrons.
Neutrons collide with nitrogen-14 in the atmosphere to create Carbon-14
Carbon-14 emits beta-minus decay and becomes Nitrogen-14.
N=N₀e^-λt
(number of CURRENT un-decayed nuclei) = (number of INITIAL un-decayed nuclei) × e ^ -(Decay constant × Time)
Name 3 fundamental particles
Quarks, Neutrinos and Electrons
State 2 qualities of radioactive decay
random and spontaneous
Summarise PAG 7.1 - 'Observing radioactive decay's random nature'
Set up the clamp stand and attach the GM tube to it, making sure to keep the GM tube connected to the counter.
Before moving the radioactive source into the room you will be working in, you must calculate the background count by switching on the counter (connected to the GM tube) for at least 30 seconds. Record this background count.
Remove the radioactive source from its storage box using long-handled tongs and place it 0.1 m away from the GM tube in the source holder.
Switch on the counter and take readings of count for 10 seconds every 30 seconds for 5 minutes. When recording readings, you should subtract the background count from the recorded value to produce a corrected count rate.
Repeat this procedure twice more with a new source, after waiting for at least 5 minutes between repeats, and find the average count for each reading.
Summarise PAG 7.2 - 'Investigating the absorption of ionising radiation'
Before moving the radioactive source into the room you will be working in, you must calculate the background count by switching on the counter (connected to the GM tube) for at least 5 minutes. Record this background count.
Using the tongs place the source about 5 cm from the Geiger counter, and measure the count rate after 5 minutes. Calculate the corrected count rate. (Corrected count rate is the difference between measured count rate and background count).
Place a few sheets of paper in front of the source and repeat the step above.
If the corrected count rate drops to 0 we can assume the source was emitting only alpha radiation, if there is a significant drop we can assume it was emitting partly alpha radiation.
Repeat the above step using the aluminium foil and 4 cm of lead. If there is a significant decrease in count rate for aluminium foil, then beta radiation is being emitted and if there is a significant decrease in count rate for the lead block, then gamma radiation is being emitted.
Repeat this procedure for each of the sources to identify the types of radiation they're emitting.
Summarise PAG 7.3 - 'Determine half-life using an ionisation chamber'
Set up the ionisation chamber, connecting it to the DC voltage source and ammeter as shown in the diagram below:
Remove the radioactive source from its storage box and place it in its holder in front of the ionisation chamber. Immediately start the stopwatch.
Record the ionisation current every 10 seconds for 3 minutes.
Repeat this procedure twice more with a new source after waiting for at least 5 minutes between repeats, and find the average current for each reading.
What are hadrons?
Any hadron made up of 3 quarks
What are Hadrons?
Particles and antiparticles that are affected by the strong nuclear force
What are Leptons?
Particles and antiparticles that are not affected by the strong nuclear force e.g. electrons, neutrinos and muons
What are mesons?
Any hadron made up of a quark and anti-quark
What are the 3 quarks you need to know (excluding their antiparticles)?
Up, Down and Strange
What are the 4 fundamental forces?
Gravitational, Electromagnetic, Weak nuclear, Strong nuclear
What are the limitations of carbon dating?
Assumes that the ratio of carbon-14 : carbon-12 remained constant over time. This may have increased overtime due to burning fossil fuels and volcanic eruption. May also be altered due to solar flares or testing of nuclear bombs
Activity of carbon-14 is very small that it is comparable to background count rate
What are the particles in beta-minus decay
neutron -> proton + electron + electron antineutrino
What are the particles in Beta-plus decay
proton -> neutron + positron + electron neutrino
What are the three types of neutrino?
Electron neutrino, Muon neutrino, Tau neutrino
What can be used instead to date rocks and meteors?
Decay of Rubidium-87
What does alpha radiation consist of?
2 protons, 2 neutrons w/ a charge of +2e
What does beta radiation consist of?
fast-moving electron/positron
charges:
plus = +e
minus -e
What does gamma radiation consist of?
high energy photons that travel at the speed of light and carry no charge
What is a fundamental particle?
A particle that has no internal structure and cannot be divided into smaller parts.
What is an atomic mass unit (u)?
1/12th the mass of a carbon-12 atom
What is Carbon Dating?
Determining the age of organic matter from the proportions of carbon-12 and carbon-14 isotopes that it contains.
What is one atomic mass unit equal to?
1.661 x 10^-27 kg
What is the activity of a source?
The rate at which active nuclei in a sample decay
What is the antiparticle of a neutrino?
Antineutrino
What is the antiparticle of a neutron?
Antineutron
What is the antiparticle of a proton?
Antiproton
What is the antiparticle of an electron?
Positron
What is the charge of a Down (d) quark?
-1/3 e
What is the charge of a strange (s) quark?
-1/3 e
What is the charge of an Up (u) quark?
+2/3 e
What is the decay constant?
The probability of an individual nucleus decaying per unit time
What is the equation for alpha decay?
What is the equation for beta-minus decay?
What is the equation for beta-plus decay?
What is the equation for gamma decay?
What is the half-life of an isotope?
The average number of time it takes for half the number of the active nuclei in the sample to decay
What is the half-life of Carbon-14?
5700 years
What is the ratio of Carbon-14 to Carbon-12 (C-14 : C-12) and is it the same in all things?
1.3 × 10⁻¹²
What is the relationship between the decay constant and half-life?
Inversely Proportional
What is the strong nuclear force?
The force that binds nucleons together
What is the unit of activity?
Becquerel (Bq)
What must you do when transferring radioactive material?
Seal it in a lead-lined container as this absorbs the radiation, limiting its penetration
Note
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