Nuclear Physics

Question 1

Dalton’s atom model

Answer 1

Small, round, indestructible piece of mater - the smallest thing possible

Question 2

Plum Pudding model

Answer 2

J.J. Thompson’s model - He envisioned atoms as “negative particles” (electrons - he didn’t know he had discovered them at the time) in a “sea of positivity”

Question 3

Rutherford’s gold foil experiment (process)

Answer 3

Shot alpha particles at a sheet of very thin gold foil, expecting them to all go through - some did, some deflected, some bounced off

Question 4

Rutherford’s gold foil experiment (conclusions)

Answer 4

• The majority of an atom is empty space
• There must be a concentrated positive charge (nucleus)
• The majority of the mass of an atom must be concentrated in a very small space (nucleus)

Question 5

Define Radioactivity

Answer 5

Atoms that are 𝗿𝗮𝗱𝗶𝗼𝗮𝗰𝘁𝗶𝘃𝗲 have 𝘂𝗻𝘀𝘁𝗮𝗯𝗹𝗲 𝗻𝘂𝗰𝗹𝗲𝗶 that 𝘀𝗽𝗼𝗻𝘁𝗮𝗻𝗲𝗼𝘂𝘀𝗹𝘆 𝗯𝗿𝗲𝗮𝗸 𝗱𝗼𝘄𝗻 to become more stable

Question 6

Why might an atom be unstable?

Answer 6

If it has too many neutrons, their instability will cause decay, if it has too few neutrons, the protons will be too close together and push each other apart, and if it has too much energy, it won’t be stable (like a building in an earthquake)

Question 7

What is an 𝗮𝗹𝗽𝗵𝗮 particle?

Answer 7

Also called a helium nucleus, it’s a positively charged particle with two protons, two neutrons, and no electrons. The symbol is α

Question 8

What are some of the properties of an 𝗮𝗹𝗽𝗵𝗮 particle? (speed, penetration, how far it goes without ionizing)

Answer 8

Travels at about 10% of the speed of light
Only travels about 10 cm before ionizing into He gas - rips electrons off of other things. It’s great at ionizing because of its very positive charge and (relatively) large mass
Blocked by paper

Question 9

Alpha decay formula

Answer 9

__A A-4 4
X —–> Y + α
Z Z-2 2

Question 10

What is a 𝗯𝗲𝘁𝗮 particle?

Answer 10

A beta particle is a high speed electron which is formed when a neutron spontaneously decays into a proton. Its symbol is β or e.

Question 11

What are some of the properties of a 𝗯𝗲𝘁𝗮 particle? (speed, ionizing, penetration)

Answer 11

It travels at about 2.9x10⁸ m/s - almost the speed of light
Medium penetration - blocked by 3 or so mm of aluminum (absorbed by it)
Medium ionizing - it knocks off electrons from other atoms and/or attaches to them. Its -1 charge and tiny mass make ionizing more difficult.

Question 11

Beta decay formula

Answer 11

__A A+0 0
X —–> Y + α
Z Z+1 -1

Question 12

What is a gamma ray?

Answer 12

A gamma ray is a high energy electromagnetic wave with a very small wavelength - it’s not a particle. It’s caused by particles having excess energy and (often?) accompanies other types of radiation. It’s represented by γ or ૪ (but the y is probably better).

Question 13

What are some properties of a gamma ray? (speed, ionizing, penetration)

Answer 13

Travels at the speed of light
Terrible at ionizing because it has no mass or charge, but it has the ability to ionize by knocking electrons off of atoms due to its high speed. This makes it dangerous.
Highest penetrative power (because of its bad ionizing) - blocked by several cm of lead or several m of concrete

Question 14

Gamma radiation formula

Answer 14

A A 0
X –> Y + γ
Z Z 0
No mass or charge means X is the same as Y but Y has less energy

Question 15

How does a little radiation often cause harm?

Answer 15

Cell mutation can cause cell death, genetic mutation, and cancer by mutating the DNA of the cell. If the self regulation is impaired, it can lead to cell death and cancer.

Question 16

What is it called when you get a lot of radiation all at once in your body?

Answer 16

Acute radiation sickness

Question 17

What is the first stage of acute radiation sickness?

Answer 17

Prodromal stage - nausea, cognitive impairment, vomiting, fatigue, diarrhea, headache, fever.

Question 18

What is the second stage of acute radiation sickness?

Answer 18

Latent stage - you start feeling better
UNLESS you got 8+ gray, in which case you skip this stage

Question 19

What is the third stage of acute radiation sickness?

Answer 19

Manifest Illness - Longer term symptoms/problems set in (unless you got a super high dose, in which case you have 48 hours to live)

Question 20

What is the fourth stage of acute radiation sickness?

Answer 20

Recovery or death

Question 21

How is ionizing harmful?

Answer 21

If a particle/ray comes in contact with your cells, it will rip off electrons off of them, messing up the DNA.

Question 22

How do alpha particles deflect in an electric field?

Answer 22

Towards the negative plate

Question 23

How do beta particles deflect in an electric field?

Answer 23

Towards the positive plate

Question 24

How does a gamma ray deflect in an electric field?

Answer 24

It passes through unaffected

Question 25

When in a magnetic field or an electric field, the particles must be travelling ________ to the field.

Answer 25

Perpendicular, at right angles to

Question 26

Which direction is the magnetic field facing?
x x x x
x x x x
x x x x

Answer 26

Into the screen/page

Question 27

Which direction is the magnetic field facing?
. . . .
. . . .
. . . .

Answer 27

Out of the screen/page, towards me

Question 28

How does a gamma ray deflect in a magnetic field?

Answer 28

It passes through unaffected

Question 29

What is the right hand slap rule? (3 parts)

Answer 29

4 long fingers - direction of the magnetic field
Thumb - Direction of moving charge
Palm - force on positive charge (back of hand for negative)

Question 30

How many microsieverts are in a sievert?

Answer 30

1,000,000

Question 31

Define Background radiation

Answer 31

The (average) level of radiation detectable as part of everyday life, due to manmade and natural sources

Question 32

What are the 5 sources of background radiation?

Answer 32

Food, rocks and building materials, radon gas, cosmic rays, and artificial sources like medical procedures and nuclear tests

Question 33

Half-Life definition

Answer 33

The time taken for half of the nuclei in a sample of radioactive material to decay

Question 34

Is half-life perfectly accurate? Why or why not?

Answer 34

No - All decay is random and spontaneous, so you can’t predict when an individual nuclei will decay. Half life is a probability of when half a sample has decayed.

Question 35

How many half lives does it take for a substance to be considered depleted?

Answer 35

5 - most has been used up (around 99% ish)

Question 36

Half life formula and what n represents

Answer 36

Number of remaining nuclei = Original amount/2n. N is the number of half lives that have happened

Question 37

What do the dotted lines on a half life graph represent?

Answer 37

The half lives - after a specific time period, you’ll have half of it left

Question 38

What could the Y axis on a half life graph be?

Answer 38

Nuclei number (as in how many), count rate, mass

Question 39

What is the x axis on a half life graph?

Answer 39

Time (in a unit)

Question 40

What are the applications and uses of radiation?

Answer 40

Smoke detectors, thickness measurements/quality control, fault detection in pipes, food irradiation, cancer treatment, organ function/ bloodflow testing, and sterilisation

Question 41

Greater deflection in an electric field means the mass is…

Answer 41

Smaller

Question 42

If a scientist measures radiation and doesn’t subtract the background radiation, the results will have a _____________ error.

Answer 42

Systematic

Question 43

Define contamination (in terms of radioactivity)

Answer 43

Unwanted presence of materials containing radioactive atoms on other materials

Question 44

Define irradiation (in terms of radioactivity)

Answer 44

The process of exposing something to nuclear radiation - irradiated stuff DOES NOT become radioactive

Question 45

How should alpha emitters be safely stored?

Answer 45

In a thin package (though the handler should still wear protective clothing so it doesn’t get inside you)

Question 46

How should beta emitters be safely stored?

Answer 46

In a lead/other dense metal container

Question 47

How should gamma emitters be safely stored?

Answer 47

In a very thick lead/other dense metal container and/or deep underground

Question 48

How does time affect the radiation you receive?

Answer 48

The less time you spend around an emitter, the less radiation you will receive because less particles will have time to react with you

Question 49

How does distance affect the radiation you receive?

Answer 49

The further away you are, the less radiation you will receive because the radiation spreads out and won’t be concentrated as it hits you - less will hit you overall

Question 50

How does shielding affect the radiation you receive?

Answer 50

Shielding will protect you by blocking (at least some of) the radiation, meaning that you will receive less radiation.

Question 51

Define nuclear fission

Answer 51

The splitting of large nuclei into smaller nuclei, releasing energy in the process

Question 52

Define nuclear fusion

Answer 52

The joining of smaller nuclei into larger nuclei, releasing energy in the process

Question 53

How does nuclear fission make energy?

Answer 53

One of the reasons for nucleus instability in an atom is having too much energy - when that happens, the energy is released when it splits apart.

Question 54

How does nuclear fusion make energy?

Answer 54

Exothermic reaction!

Question 55

Why is nuclear fusion so much more difficult to do than nuclear fission?

Answer 55

Fission sets off a nuclear chain reaction - once it’s going, it will keep going. Fusion, however, requires a lot of energy and pressure to fuse the helium isotopes because they’re both positive and want to repel each other.

Question 56

Where does the energy come from? (think of E=mc²)

Answer 56

The products of the reaction have less mass than the reactions - mass is converted into energy. This is shown with Einstein’s formula, E=mc², which shows that as the reactants turn into products, the mass lost x c² is equal to the energy gained. Even with tiny changes in mass make a huge amount of energy because c² is such a big number.