Week 8 - Radioactivity and Nuclear Interaction With Matter

Question 1

Define Radioactivity; what causes it?

Answer 1

Spontaneous emission of radiation as a result of decay / disintegration of unstable nuclei

Question 2

Define a half-life

Answer 2

Time it takes for half of any given number of radioactive nuclei decay

Question 3

Define the types of radioactivity; their penetrating ability (energy) and provide material examples

(3)

Answer 3

Alpha particles, Beta particles and Gamma rays; LOW - barely penetrating (piece of paper), MEDIUM - a little bit of penetration (few mm of Al), HIGH - highly penetrable (several cm of lead)!

Question 4

What are the rules of decay?

(3)

Answer 4

1. The sum of A (mass numbers) MUST BE THE SAME on both sides of the equation
2. the sum of Z (atomic numbers) MUST BE THE SAME on both sides of the equation
3. Conservation of mass-energy nd conservation of momentum must hold (stay true)

Question 5

Define a decay constant; what is the formula?

Answer 5

the # of particles that decay in a given time;
ΔN = -λ N Δt

Question 6

Define the decay rate; what is the formula?

Answer 6

The decay rate or activity, R, of a sample is defined as the number of decays per SECOND
R= ΔN / Δt = λN

Question 7

What does λ represent?

Answer 7

λ represents the decay constant; the rate at which a material will decay

Question 8

difference between x-ray and gamma ray?

Answer 8

gamma produced inside nucleus;
x-ray (refer to recording)