Chapter 7

Question 1

Alpha particle: composition, range and ionising abaility

Answer 1

• Helium nucleuis (2 protons and 2 electrons)
• Low penetration because of large mass/charge - a few cm of paper
• Very highly ionising - because of large charge

Question 2

Beta particle: composition, range and ionising abaility

Answer 2

• High energy electrons
• Moderate penetration- 25cm air or a few cm of body tissue
• Moderately highly ionising

Question 3

Gamma particle: composition, range and ionising abaility

Answer 3

• Very high frequency EM radiation
• Highly penetrating - meters of concrete or a few cm of lead
• Poorly ionizing - secondary ionisation

Question 4

Which particles do NOT have discrete energy values: alpha, beta, gamma

Answer 4

Beta

Question 5

Define binding energy of a nucleus

Answer 5

The minimum energy/work required to complete ly seperate the nucleons of a nucleus.

Question 6

Why are nucleus with higher amounts of nuetrons more stable than protons.

Answer 6

• Protons are charged and thus repel each other
• Neutrons do not repel each other and still contribuite to binding energy

Question 7

Define atomic mass unit (amu)

Answer 7

1/12 the mass of an atom of carbon-12

Question 8

Define isotopes

Answer 8

Nuclei of the same element, with the same proton number but diffferent number of neutrons

Question 9

Define radioactive halflife

Answer 9

The time for the activity of a sample to reduce by half

Question 10

State what is meant by ionisation

Answer 10

Addition or Removal of electrons from atom/molecule, thus causing it to gain a certain charge

Question 11

What is radioactive decay

Answer 11

Unstable nuclei spotaniously emitting energy, by the emission of an alpha, beta or gamma particle/ray. Decay is also random, meaning that you can’t tell which molecule will decay at any time.

Question 12

What is an exchange particle?

Answer 12

A particle that transmits one of the fundamental forces

Question 13

2 properties of strangeness

Answer 13

• Conserved in strong nuclear interaction
• Not always conserved in weak interaction

Question 14

What is meant by a virtual particle

Answer 14

• Intermediate particle in a feyman diagram
• Not directly observed
• temperarily violates energy/momentum conservation

Question 15

Define nuclear activity?

Answer 15

Number of disintegrations per second in a substance (also refered to as radioacitivty)