NUCLEAR PHYSICS

Question 1

who created the plum pudding model

Answer 1

• J.J. Thomson in 1904

Question 2

how does the plum pudding model work

Answer 2

• the positive charge and most of the atom’s mass is evenly distributed across the whole atom
• negatively charged electrons are dotted throughout like raisins, or plums, in a pudding

Question 3

what did Rutherford scattering demonstrate

Answer 3

• the existence of a nucleus

Question 4

how did Rutherford scattering work

Answer 4

• narrow beam of alpha particles aimed at a thin piece of gold foil, measured their angle of deflection using a microscope

Question 5

what were the results found with rutherford scattering

Answer 5

• most alpha particles passed straight through with no deflection, suggesting most of the atom was empty space
• a small number of alpha particles were deflected by a large angle, and some even bounced back, which suggested that the atom’s mass and positive charge were concentrated in a small region

Question 6

why does the rutherford scattering oppose plum pudding model

Answer 6

• if the plum pudding model was true, the particles would be deflected by a very small amount when passing through, however this was not the case
• large angle deflection occured

Question 7

how small is the radius of a nucleus

Answer 7

• 10,000 times smaller than radius of an atom

Question 8

what is radiation?

Answer 8

• where an unstable nuclei emits energy in the form of EM waves or subatomic particles in order to become stable

Question 9

what the ionising level of alpha radiation?

Answer 9

• very strongly ionising

Question 10

is alpha radiation deflected in a magnetic field?

Answer 10

• yes

Question 11

what is alpha radiation absorbed by?

Answer 11

• paper

Question 12

how can we measure the amount of ionising radiation?

Answer 12

• using a Geiger Tube

Question 13

how does a Geiger Tube work

Answer 13

• when ionising radiation enters the tube, it creates free charges, which are attracted to the electrodes
• this generates a pulse of charge, measured as counts

Question 14

what is meant by count rate?

Answer 14

• numher of counts measured per second / minue

Question 15

what happens if theres no radioactive source present inside the tube?

Answer 15

• we still measure a count rate due to background radiation

Question 16

what is a cloud chamber

Answer 16

• box filled with air saturated with water vapour