Particle Physics

Question 1

Nucleon Number (mass number)

Answer 1

Total number of protons and neutrons in the nucleus

Question 2

Proton Number (atomic number)

Answer 2

Number of protons in the nucleus

Question 3

Rutherford Scattering Experiment

Answer 3

Positively charged alpha particles fired at a thin sheet of gold leaf
In a vacuum
Most went straight through
Some were deflected
A few were reflected along their original path
Suggests an atom is mainly empty space
With the nucleus containing most of the mass
The nucleus is very small and charged, with distant orbiting electrons

Question 4

Why were the alpha particles fired in a vacuum in Rutherford’s experiment?

Answer 4

Prevent scattering and absorption of alpha particles by the air

Question 5

Linear Accelerators

Answer 5

Accelerates charged particles in a straight line
Use alternating PD
Electric field between adjacent drift tubes is always in the right direction to accelerate ions
Drift tubes get longer as AC supply has a constant frequency and the ions are speeding up

Question 6

Cyclotrons

Answer 6

Potential difference (E field) gives particles energy- they accelerate
Constant frequency
PD switches every half cycle as alternating
Magnetic field at right angles to particle path
Centripetal force- circular motion
Radius of circle increases as particle gets faster

Question 7

Synchotrons

Answer 7

Potential difference (E field) gives particles energy- they accelerate
Constant frequency
PD switches every half cycle as alternating
Magnetic field at right angles to particle path
Centripetal force- circular motion
B field varies so particles follow a circular path rather than spiral

Question 8

Why does thermionic emission occur?

Answer 8

Metal heated, electron gains energy
Leave the surface of the metal
Accelerates in an E or B field

Question 9

How do you work out the velocity of a particle accelerated through a potential?

Answer 9

VQ=0.5mv^2

Question 10

Antimatter characteristics

Answer 10

Same mass as corresponding particle
Opposite charge
Opposite quantum numbers

Question 11

How do you work out the energy of a moving particle near the speed of light?

Answer 11

E=mc^2 and KE

Question 12

What happens in an annihilation event?

Answer 12

Particle meets antiparticle
Annihilate
Mass converted so only energy is left in the form of photons

Question 13

Electron Volt

Answer 13

Energy required to accelerate an electron through a potential difference of 1V

Question 14

Baryon

Answer 14

Made of 3 quarks

Charge is the sum of the quarks

Question 15

Meson

Answer 15

2 quarks

Quark-antiquark pair

Question 16

Lepton

Answer 16

Fundamental particles

Electron, tau, muon

Question 17

5 Conservation Laws for particle interactions

Answer 17

Energy
Momentum
Charge
Baryon number
Lepton number

Question 18

Bubble Chamber

Answer 18

Track seen made up of bubbles
Which reflect light
Produced as the electron ionises the superheated hydrogen liquid

Question 19

Cloud Chamber

Answer 19

Dry ice (CO2) means cold chamber at the bottom
Put volatile liquid in
Evaporates, saturates the air
Particles provide condensation nuclei

Question 20

Geiger-Muller Tube

Answer 20

No current between plates
Ionising radiation
Current flows
Mica used as alpha can get through but gas particles can’t