Particle Physcis

Question 1

What were the observations from the alpha scattering experiment?

Answer 1

• most of the alpha particles passed straight through the thin gold foil with very little scattering.
• very few of the particles deflected through angles of more than 90.

Question 2

What were the conclusions from Rutherford alpha scattering experiment?

Answer 2

• most of the atom is mostly empty space and so the mass must be concentrated at some point within the atoms.(nucleus)
• the atoms has a small dense nucleus which contains most of the mass of the atom and is positively charged.

Question 3

Explain the nature of the strong nuclear force?

Answer 3

It acts between all nucleons and all quarks, it counteracts the repulsive electrostatic forces between protons in the nucleus.
- it is attractive at small distance (up to 3fm) and repulsive below 0.5fm and has limited range

Question 4

What are hadrons?

Answer 4

• Hadrons are particle made up of quarks.
• they are affected by the strong nuclear force
• they decay by the weak nuclear force

Question 5

What are leptons?

Answer 5

They are elementary particles not affected by the strong nuclear force

Question 6

4 reasons why a nucleus would decay?

Answer 6

• too many neutrons
• too many nucleons in total (too heavy)
• too few neutrons (too many protons)
• too much energy in the nucleus

Question 7

How does a nucleus decay

Answer 7

It decays by releasing energy and particles until it reaches a stable form

Question 8

What can we model radioactive decay as?

Answer 8

Random and spontaneous

Question 9

What does it mean when we model radioactive decay as random?

Answer 9

• cannot predict when a nucleus will decay

- each nucleus has the same probability of decaying per unit time

Question 10

What does it mean when we model radioactive decay as spontaneous?

Answer 10

• not affected by the presence of other nuclei

- not affected by external factors like pressure or temperature

Question 11

Difference and similarity between particles and anti-particles?

Answer 11

Sim- mass

Diff - charge

Question 12

What is beta minus decay?

Answer 12

When a neutron turns into a proton, the atoms releases and electrons and a neutrino

Question 13

What quantities must be conserved during the decay of particles?

Answer 13

Charge,mass and baryon number

Question 14

What is most ionising radiation?

Answer 14

Alpha

Question 15

How far does a beta particle typically penetrate in air?

Answer 15

50cm

Question 16

What is the activity of a source?

Answer 16

The number of radioactive decays per second