4.6 Nuclear Decay

Question 1

3 Types of Radiation

Answer 1

Alpha Particle
* 2 protons
* 2 neutrons
* ⁴₂α
* Mass approx 4u

Beta Particle
* 1 electron
* ⁰_-1β
* Mass approx 0.00055u

Gamma-Ray
* Electromagnetic wave of very short wave length
* ⁰₀γ
* Mass 0

Question 2

Define

Radioactive Decay

Answer 2

This is the spontaneous disintegration of an unstable nucleus. The decau process is completely random.

Question 3

Define

Decay Constant, λ

Answer 3

The decay constant, λ, for a sample of unstable nuclei is the probability of an individual nucleus decaying within unit time.

Units s^-1

Question 4

Define

Activity, A

Answer 4

The activity of a source is the number of nuclei which decay in unit time.

Units s^-1

Question 5

Equation

Activity, A

Answer 5

A = λN

A is activity
λ is the decay constant
N is the number of undecayed nuclei

Question 6

Equation

Exponential Decay Law

Answer 6

N = N₀e^-λt

N is the number of undecayed nuclei.
N₀ is the inital number of undecayed nuclei.
λ is the decay constant.

Question 7

Define

Half-Life

Answer 7

Half-life is the time taken for half the radioactive nuclei to decay.

Question 8

Equation

Corrected count rate

Answer 8

Actual reading - Background count