modern physics

Properties of alpha particles

Mass= 4 amu

Charge= +2 (2P + 2N) = He nuclei

Short range (stopped by paper or 5 cm of air)

High biological damage

Properties of Beta particles

Mass≈ 0 amu

Charge= -1 = electron (e-)

Medium range (3cm Al, or 30m of air)

Medium biological damage

Properties of gamma particles

Mass= 0 amu

Charge= 0

High energy photon (ElectroMagnetic EM wave) I.e. radio wave, UV rays

Long range (30cm Pb or several Km of air)

Low biological damage

Which type of natural radioactivity is the most dangerous? Why?

Alpha radioactivity, because even a small amount of exposure has the capability of killing a person, they will destroy so many cells than your body will be unable to recover

Nuclear decay of Alpha particles \frac{222}{86}Rn->\frac{218}{84}Po+He

Nuclear decay of beta particles \frac{218}{84}Po->\frac{218}{85}At+\frac{0}{-1}e

What is nuclear fission?

Splitting heavier atoms into lighter stones by adding neutrons

What is enrichment?

Uranium 235 is used for nuclear fission and when you get the uranium in its natural state, 99.3% of it will be U 238. So enrichment is increasing the proportion of Uranium 235 isotopes.

What is critical mass?

Critical mass is the amount of Uranium 235 needed for a chain reaction to be sustained.

What does a moderator do

Moderators are substances that slow down neutrons so that they may be absorbed by the uranium to continue the reactions. Heavy water is a good moderator as it has a low atomic mass and does not absorb the neutrons.

What is a control rod

Control rods control the rate of reaction by inserting substances that absorb the neutrons. So to keep the reaction occurring at a safe rate.

What are advantages of fission

• Produce a lot of energy with very little fuel

• No green house gases while producing energy continuously without the need for wind or light

What are the disadvantages of fission

• highly radioactive

• Events like Chernobyl have occurred when the reactions are not controlled

What is the emergency shut down of a reactor called? And how is it done in Canadian reactors?

It is called a scram. In Canadian reactors there is two shut down systems, the first system drops all control rods into the reaction to absorb enough neutrons that the reactions can no longer be sustained. The second system injects a neutron absorbing solution into the heavy water.

What is fusion, what is the fuel and what is its waste product?

When light elements combine to produce heavier ones. It’s fuel is hydrogen, and it’s waste is He.

What are the advantages of fusion

• Byproduct are harmless

• incredibly safe (if you hit the machine it would stop the reaction, it’s that sensitive)

• Fuel is cheap and easy to obtain(its everywhere and very abundant all over the universe)

What are the disadvantages of fusion

• at the moment we haven’t produced more energy than we have put in

• Otherwise none

How are elements turned into unstable radioactive ones? Why do we do this? Isn’t radioactivity bad?

Elements are turned into unstable ones by neutron bombardment. We do this to get the energy it emits, radiation can be bad if it’s exposed to you, but in a controlled environment it’s fine. Also we get exposed to radiation everyday from the sun

According to quantum mechanics are atoms particles or waves? Explain

They are both, they behave like waves or particles depending on how it is observed

What does “measurement determines reality” mean

The act of observing or measuring a particle forces it to choose a single state rather than acting in multiple as a superposition.

Why is it possible to travel to the future but not the passed?

In Einstein special relativity you can experience time dilation, the faster you move the slower your clock runs compared to others, this is the same for the stronger the gravity you are in. This cannot be done inversely because time only moves forward.

What is gravity

Mass causes space-time to be curved, the force of gravity is an illusion caused by objects moving on a straight path on a curved surface.

What is dark matter, why do we think it exists

It is unseen mass.we think It exists because it explains why the high speeds of other galaxies and solar systems, for example in other solar systems the further away you are from the center the faster or about the same speed you go

Why was the discovery of Higgs boson exciting?

It completes the standard model, if it didn’t exist that would mean everything is massless. And it explains why particles have mass.

What is an electrical and gravitational fields, what do they do? Why are they needed

Electric charges modify the properties of space. That’s an electric field. Fields explain how forces can be applied to charges without needing to be in contact with the source of the force.

Fission vs fusion as sources for electrical energy

• Fusion releases more energy per reaction than fission. (3 to 4 times more)

• Each generate mass amounts of energy by converting part of their mass into heat - E=mc²