Nuclear

Question 1

On an NZ graph where is β+/- decay and where is alpha decay?

Answer 1

β+ below line to change protons to neutrons
β- above line to change neutrons to protons
Alpha large nuclei. Top corner of graph

Question 2

In beta + and beta minus decay what other particles are given off?

Answer 2

Beta + electron neutrino

Beta - electron anti neutrino

Question 3

Give the range of values and the unit of the y axis on a binding energy graph.

Answer 3

0-10 MeV

Question 4

Give two examples of moderators in nuclear fission reactors and why do we need moderators?

Answer 4

Water and graphite

Slow down/absorb neutrons to increase probability of collision and further reaction

Question 5

What are control rods normally made from and why are they needed?

Answer 5

Boron

Absorb neutrons to decrease rate of reaction

Question 6

Define binding energy

Answer 6

The energy needed to separate all the nucleons in a nucleus

Question 7

Give five sources of background radiation

Answer 7

Cosmic rays, the sun, radon, nuclear fallout, c-14

Question 8

Give the conclusions of rutherfords scattering experiment.

Answer 8

Nuclei must be positive to repeal alpha particles.

Nuclei must be small since very few alpha particles are deflected by large angles-must pass straight through foil.

Most of the mass and positive charge must be in nucleus because most alpha particles pass straight through

Question 9

How can you use rutherfords scattering experiment to estimate the radius of the nucleus?

Answer 9

Alphas that are deflected straight back must be stationary at short distance from nucleus. At this point electric potential energy is equal to initial kinetic energy. Use equation for potential energy (potential times charge) to get r (distance of closest approach)

Question 10

What is a more accurate method than rutherfords scattering experiment to calculate the radius of a nucleus?

Answer 10

Electron diffraction

Question 11

In the electron diffraction experiment give the equation for when the first minimum occurs

Answer 11

Sinθ=1.22λ/d. Where theta is the scattering angle and d is the diameter of the nucleus

Question 12

Give the value of r0

Answer 12

1.4x10^-15

Question 13

Define the atomic mass unit

Answer 13

1/12 the mass of carbon 12

Question 14

Give the definition of the decay constant

Answer 14

Probability of a specific nuclei decaying per unit time

Question 15

Give the definition of activity

Answer 15

The number of unstable nuclei in a radioactive sample that decay each second

Question 16

Define critical mass

Answer 16

The amount of fuel needed for a fission reaction to continue at a steady rate in its own

Question 17

Define half life

Answer 17

The average time it takes for the number of unstable nuclei in a sample of radioactive isotope to halve

Question 18

Name the substance used in medical diagnosis and explain why it is good for this use.

Answer 18

Technetium-99m

Emits gamma, can easily be made in hospitals when needed, has half life of 6 hours, and decays to a more stages isotope