Nuclear

Question 1

In Rutherford scattering experiment, what does the fact that most alpha particles pass straight through the foil or are scattered slightly conclude to?

Answer 1

The atom must be mostly empty space, with a small nucleus

Question 2

In Rutherford scattering experiment, what does the fact that some alpha particles are deflected by very large angles (>90 degrees) conclude to?

Answer 2

Most of the mass must be in the nucleus, and the nucleus must have a large positive charge

Question 3

State 3 disadvantages of the closest approach method

Answer 3

• alpha particle measurements are disturbed by nuclear recoil
• alpha particle measurements are disturbed by the SNF when coming close to the nucleus, where as electrons are not effected by the SNF
• alpha particles are scattered only by the protons and not all the nucleons that make up the nucleus

Question 4

State 1 disadvantage of the electron diffraction method

Answer 4

The first minimum of the diffraction pattern is often difficult to determine as it supposes on other scattering events

Question 5

What is the value of R0, and what does it represent?

Answer 5

Approx 1.4 x10^-15 m, and its the radius of a hydrogen nucleus

Question 6

What are the constituents of the 4 types of radiation?

Answer 6

Alpha: 2 protons, 2 neutrons
Beta -: electron
Beta +: positron
Gamma: higher frequency EM wave

Question 7

What is the penetrating power of the 4 types of radiation?

Answer 7

Alpha: low
Beta: medium
Gamma: high

Question 8

What is the range in air for the 4 types of radiation?

Answer 8

Alpha: approx 5cm
Beta -: 1-2m
Beta +: annihilates almost instantly
Gamma: infinite

Question 9

State 3 sources of background radiation

Answer 9

• cosmic rays
  -nuclear waste
  -X-rays

Question 10

What is meant by the random nature of radioactive decay?

Answer 10

You cannot predict when a particular nucleus will decay

Question 11

Define the decay constant

Answer 11

The probability of a nucleus decaying per second

Question 12

Define activity

Answer 12

The number of unstable nuclei decaying per second

Question 13

State 3 limitations of carbon dating

Answer 13

• for man made objects, you can only find the age of the material not the object
• objects may have been contaminated by other radioactive sources
• there is uncertainty of the ratio of carbon-14 to carbon-12 thousands of years ago

Question 14

Define the atomic mass unit

Answer 14

1u = 1/12 the mass of an atom of carbon-12

Question 15

Define mass defect

Answer 15

The difference between the mass of a nucleus and its constituents

Question 16

Define binding energy

Answer 16

The amount of energy required to separate a nucleus into its separate nucleons

Question 17

What is nuclear fission?

Answer 17

When a nucleus splits into 2 smaller daughter nuclei, releasing energy and several fast moving neutrons in the process

Question 18

What is nuclear fusion?

Answer 18

When 2 smaller nuclei join to make a larger one, releasing energy in the process

Question 19

Why is nuclear fusion so hard to achieve?

Answer 19

Electrostatic repulsion between 2 nuclei must be over come

Question 20

What is the function of fuel rods and what isotopes do they contain and in what proportion?

Answer 20

They contain the fuel required for fusion, and they consist of approx 5% of U-235 and 95% of U-238

Question 21

What is the function of the moderator, and what is it made from?

Answer 21

Slows down the neutrons via elastic collisions, its made from water or graphite usually

Question 22

What is the function of control rods, and what are they made from?

Answer 22

Absorbs neutrons to keep the rate of reaction steady, usually made from boron

Question 23

What is the function of the coolant, and what is made from?

Answer 23

Removes the heat produced by fission and then produces steam which drives turbines, usually water

Question 24

What is the function of the shielding, and what is it made from?

Answer 24

The concrete casing around a reactor core, reduces the intensity of the radiation from neutron and gamma emission in particular

Question 25

What is the most dangerous part of neuclear waste and why?

Answer 25

Used fuel rods, they emit beta and gamma radiation