Nuclear And Particle Physics

Question 1

Rutherford’s observations and conclusions

Answer 1

• The atom is mainly empty space as when alpha particles were shot at gold foil they pass through undisturbed
• The nucleus has a large positive charge charge as alpha particle were deflected less than 90 degrees
• The nucleus is small as some alpha particles were deflected at angles greater than 90 degrees

Question 2

Strong nuclear force

Answer 2

• A force that acts between all nucleons with a very short range
• The force is repulsive below 0.5fm
• The force is attractive to about 3fm

Question 3

Mean density of atoms

Answer 3

10³ kgm⁻³

Question 4

Mean density of nuclei

Answer 4

10¹⁷ kgm⁻³

Question 5

Hadrons

Answer 5

A particle or antiparticle affected by the strong nuclear force and weak nuclear force (causes decay). Eg protons and neutrons

Question 6

Lepton

Answer 6

Particle and antiparticles that are not affected by the strong nuclear force but affected by the weak nuclear force e.g. Electrons and neutrinos

Question 7

Quark model for a proton

Answer 7

uud

Question 8

Quark model for a neutron

Answer 8

udd

Question 9

Beta-minus decays

Answer 9

¹₀n ——> ¹₁p + ⁰₋₁e +

d ——> u + ⁰₋₁e +

= antineutrino

Question 10

Beta plus decay

Answer 10

¹₁p ——> ¹₀n + ⁰₊₁e + v

d ——> u + ⁰₊₁e + v

⁰₊₁e= positron

 v= neutrino

Question 11

How is decay described

Answer 11

Random:

• cannot be predicted when a particular nucleus will decay
• each nucleus has the same chance of decaying

Spontaneous:
-Not affected by other nuclei or external factors

Question 12

Half life

Answer 12

Average time for half the number of active nuclei in the sample to decay

Question 13

Radioactive dating/ carbon dating

Answer 13

In carbon dating the ratios of carbon 14 to carbon 12, is compared in dead matter to similar living matter.

Rations of radioactive material is used for dating

Question 14

Binding energy

Answer 14

Minimum energy required to completely separate a nucleus into protons and neutrons

Question 15

Mass defect

Answer 15

The difference between the mass of the completely separated nucleus and the mass of the nucleus

Question 16

Binding energy per nucleon

Answer 16

The greater the binding energy per nucleon the more tightly bound the nucleus/ more stable it is

Question 17

Fuel rods

Answer 17

Contain enriched uranium mainly uranium 238

Question 18

Moderator

Answer 18

• It slows down fast moving neutrons so that they can be absorbed by fuel rods. Eg water is a moderator
• The moderator also acts as a coolant which removes heat from the fuel rods

Question 19

Control rods

Answer 19

• Rods made of material that absorbs neutrons

- They are moved so that only one neutrons survives per fission to be absorbed by the next fuel rod

Question 20

Environmental impact of fission

Answer 20

The used fuel rods are toxic and have a long half life so they have to be buried deep underground. It must not enter food or water supplies

Question 21

Measuring half life (dice method)

Answer 21

• Using die roll them and every time they land on a certain face e.g. Even you remove them
• Record the number of die each turn until there are no more die
• Then plot the number of die left to the number of turns taken

Question 22

Measuring half life

Answer 22

• Using a geiger muller tube find the background count rate
• In a seal bottle mix protactinium-234 with uranium salt and shake
• Record the counts for 10s for every 30s
• Plot count rate against time