3.5 Nuclear Decay Flashcards
What is alpha radiation?
A fast moving helium nuclei ejected from certain radioactive nuclei.
What is Beta radiation?
Electrons with speeds just less than the speed of light, ejected from certain radioactive nuclei
What is Gamma (y) radiation?
Photons of high energy (high frequency, short wavelength) ejected from radioactive nuclei
What does the A ( Mass number on top) mean on the periodic table?
The number of protons plus the number of neutrons.
It is the top of the notation
What does Z (Atomic Mass) mean?
The number of protons in the atom.
What is the activity of a radioactive source?
The rate of decay (number of decays per second) of a sample of radioactive nuclei
What is the half-life?
The time taken for the number of radioactive nuclei, N (or activity) to reduce to one half of the initial value.
What is the decay constant?
The constant which appears in the exponential decay law and determines the rate of decay.
It is also related to half-life by λ = ln2/T.
Its symbol is λ
What is the equation of half-life?
N = No/2^x
or
A = Ao/2^x
Where No and Ao are the original number of nuclei and activity.
x = number of half-lives
What is the derivation of λ
We know N = Noe^-λt
No = original number of nuclei
t = time
T’ = Half-life
1) When t = Half-life (T’):
N/No = e^-λT’
N/No = 1/2
2) 1/2 = 1/e^λT’
3) 2= e^λT’
4) ln(2) = λT’
λ = ln2/T’
What is the formula of A in terms of N (Number of nuclei)
A = λN
λ = Decay constant s^-1 (ln2/Half-life)
What are the units for activity?
A = Becquerel (Bq)
1 Becquerel = 1 nuclear decay per second
How does a Geiger Miller tube work?
It consists of a tube with low pressure ionizing gas.
As ratiation passes through the tube, the gas is ionized creating a current that is detected and taken as a count.
