Unit 2 Module 3 - Nuclear physics

Question 1

Describe an experiment which investigates the size of the nucleus of an atom, and describe the properties of the incident radiation

Answer 1

Alpha particle scattering. 
Takes place in a vacuum.
Most particles have little deflection because atom is mostly empty space.
Very few large deflection. Coulombs law
Alpha repelled by nucleus
Monoenergetic

Question 2

What is the range of alpha in air?

Answer 2

1cm

Question 3

What is the range of beta in air?

Answer 3

2m

Question 4

What is the range of alpha in paper?

Answer 4

0.2mm

Question 5

What is the range of beta in aluminium?

Answer 5

1mm

Question 6

What is the range of gamma in lead?

Answer 6

1cm

Question 7

Describe an absorption experiment to distinguish between radiations

Answer 7

Use a source and Gieger Muller tube, with paper, aluminium and lead in between. Measure the background radiation activity, then remove lead, aluminium and paper in turn. If the count rate increases as they are taken away then they the radiation is known; lead is gamma, beta is aluminium and alpha is paper.

Question 8

Advantages and disadvantages of nuclear fission

Answer 8

Advantages: doesnt produce acid rain
a lot more energy per unit volume
doesnt emit CO2
Disadvantages: problems with it getting out of control
maintaining the reaction so it proceeds continuously
risks from radiation
long half life

Question 9

Explain what is meant by the statement that the strong force is a short range force and explain what this implies about the densities of nuclei of various sizes

Answer 9

force only acts between one nucleon to the next
densities of nuclei are the same no matter what the size
force holding nucleons is independent of size of nucleus

Question 10

Suggest why a beta particle energy is less than calculated

Answer 10

antineutrino also given off which has some energy

nucleus has kinetic energy

Question 11

What is the decay constant?

Answer 11

probability of decay in the next second

Question 12

What is N?

Answer 12

number of undecayed nuclei in a sample

Question 13

State the importance of gravity in making fusion reactions possible inside the sun.

Answer 13

nuclei collapse under gravity, losing potential energy and gaining kinetic energy and therefore increasing the temperature. Increases the pressure, so increases the frequency of collisions

Question 14

Describe the process of fusion

Answer 14

Very high temperatures hydrogen fuse to form helium. Positrons are emitted to conserve change, which annihilate electrons releasing electrons.

Question 15

Discuss the stability of protons

Answer 15

It is stable in a nucleus. All free hadrons are unstable. They have a half life of 10^32 years

Question 16

Discuss the stability of neutrons

Answer 16

stable in nucleus

half life of 10 mins when free

Question 17

why are solar panels not practical in deep space?

Answer 17

intensity of light too small

Question 18

explain why it is not possible to accelerate to a very high energy?

Answer 18

mass increases with speed

Question 19

how can plutonium 239 be formed?

Answer 19

uranium absorbs a neutrons a beta decays into plutonium

Question 20

what particle is emitted when plutonium decays?

Answer 20

alpha

Question 21

what is the half life of plutonium?

Answer 21

24000 years

Question 22

Describe the 3 types of radiation?

Answer 22

gamma is electromagnetic radiation, doesn’t ionise, has no charge or mass, has several km of range in air and is absorbed by 1cm of lead.
alpha is a helium nuclei, is strongly ionising, has 2+ charge and 4u mass, has 1cm of range in air and is absorbed by 0.2mm of paper.
beta is an electron, weakly ionising, has 1- charge, 1/1800u mass, has a range of 2m in air and is absorbed by 1mm of aluminium

Question 23

what does a high binding energy mean?

Answer 23

greater stability