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Modern Physics Flashcards

1
Q

What is special relativity?

A

All the laws of nature are the same in all uniformly moving reference frames.
The speed of light is a constant, independent of the motion of the light source or the observer.
Motion is relative, and time is relative.
What occurs in one reference frame may occur in a different order in another reference frame. Simultaneous events may not be simultaneous.

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2
Q

u’=(v+u)/(1+((vu)/(c^2))

What does u’, v, and u stand for?

A

u’, speed of object relative to stationary observer.
u, speed of object relative to moving “ship”
v, speed of the “ship” relative to stationary reference frame.

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3
Q

Qualities of a particle.

A

Mass and volume. Kinetic collisions. Countable. Only exist in one place (localized)

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4
Q

Qualities of a wave.

A

Wavelength and frequency. Wave interference. Continuous. Over a large space (delocalized)

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5
Q

What is the photoelectric effect?

A

Ephoton=hf-W

Where Ephoton is the incident light energy, h is Planck’s constant, f is the frequency, and W is the work function (minimum energy to displace an electron).

A photon’s energy is proportional to its frequency. It takes a minimum frequency for a photon to have enough energy to displace an electron.

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6
Q

What did Max Planck theorize?

A

He theorized that metals begin to glow because their vibrating molecules can only vibrate at certain quantities of energy.

Forces could only be in little steps at a time. Energy released is not continuous, but is discretely released in packets of energy called quanta which is directly proportional to its frequency.

Planck’s Constant, h=6.63*10^-34Js

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7
Q

What is a black body?

A

A theoretical construct that absorbs all radiation reaching it and emits radiation. It does not reflect.

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8
Q

How is light similar to both particles and waves?

A

Light shows interference patters (wave). Photoelectric effect (particle).

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9
Q

Does light possess momentum?

A

Light possesses no mass, but has momentum.

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10
Q

What are the 5 possible interactions between light and matter?

A
  1. Reflection. Perfectly elastic.
  2. Photoelectric effect. Photon may free an electron and be absorbed in the process.
  3. Compton Effect. A photon may emerge with less energy and momentum after freeing an electron. Photon has lower frequency.
  4. The photon may be absorbed by an individual atom and elevate an electron to a higher energy level within the atom. The electron remaining is in an excited state. When the electron returns, the photon is released.
  5. A photon undergoes pair creation where it is converted into two particles with mass (this conserves energy and momentum because the photon’s energy is converted into kinetic energy of the new particles and their rest mass energy). It creates a positron and en electron.

These interactions all say that light must be a particle.

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11
Q

What did Young’s double slit experiment do?

A

Demonstrated conclusively that light behaves like a wave.

Also provided a way to absorb wavelength.

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12
Q

Wave Particle Duality.

A

All quantum objects, including electromagnetic radiation and electrons can exhibit interference.

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13
Q

How do quantum objects transfer?

A

In discrete amounts called quanta. (can be thought of as parcels of energy).

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14
Q

What did Louis de Broglie first propose?

A

All classical particles have wavelike properties.

Hypothesized that a photon has momentum p=h/wavelength.
From that, a particle with momentum may have a wavelength.
wavelength=h/p=h/mv

These are known as matter waves, not electromagnetic waves.

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15
Q

What makes electron microscopes possible?

A

All classical particles have wavelike properties.

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16
Q

What are the two “golden rules” of quantum mechanics?

A
  1. If a particle can be “here” or “there”, quantum mechanics allows it to be “here” and “there”.
  2. Rule 1 works as long as you don’t observe.
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17
Q

What is Heisenberg’s Uncertainty Principle?

A

There is a limit to how accurately simultaneous measurements of the position and momentum of a quantum object can be.

The very act of trying to measure the position of an electron affects its momentum and likewise for trying to measure the momentum.

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18
Q

What is the wave function?

A

A complete description of a wave/particle. Any information that cannot be derived from the wave function does not exist.

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19
Q

If two properties are related by an uncertainty principle…

A

no measurement can simultaneously determine both properties to a precision greater than the uncertainty relation allows.

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20
Q

How do you know how many electrons an element has?

A

It has equal numbers of protons and electrons. (Assuming no ionization).

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21
Q

What is u?

A

The atomic mass unit based on carbon-12, 6p+ and 6n

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22
Q

What is standard atomic notation?

A

E is the element, z in top left is atomic mass. a in bottom left is atomic number (number of protons).

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23
Q

How do you find the number of neutrons?

A

mass#-atomic#=neutron#

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24
Q

What are isotopes?

A

Atoms of the same element that have the same atomic number but different atomic masses due to a change in its number of neutrons.

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25
What is radioactivity?
The spontaneous disintegration of a nucleus.
26
What elements are radioactive?
All above atomic# 83 and some isotopes of lighter elements.
27
What is an alpha particle?
Two protons and two neutrons. Also known as He+2 Positively charged. Slightly deflected in magnetic or electric field. Emitted at high speeds. Low penetration power (2cm in air). Can be stopped by a thin layer of paper or aluminum. Results in the original nucleus changing; atomic# falls by 2, mass# falls by 4.
28
What is beta radiation.
An electron from inside the nucleus (or positron in some cases). Greatly deflected in an electric or magnetic field. Travel at various speeds, some approach speed of light. Medium penetration power, up to 10m in air. Can penetrate several centimeters of aluminum. Results in original nucleus atomic# increasing or decreasing by 1. In beta negative decay, a neutron can decay into a proton, emitting en electron and an antineutrino (incredibly small). Or, in beta positive decay a proton can decay into a neutron, emitting a positron and a neutrino.
29
What is gamma radiation?
A type of electromagnetic wave. (Photon) High energy. Highest penetration power, 2km in air. Can penetrate a minimum of 30cm of lead. Composition of original nucleus does not change when these are emitted. Energy given off in very short wavelengths (high frequency). No mass. Travel at speed of light. No charge. Often occurs alongside alpha or beta decay. Often omitted in equations. Gamma decay is a nucleus going from an excited state to a ground state.
30
What are neutrinos?
Similar to electrons, but carry no charge.
31
What radiation is the most penetrating?
Gamma. Followed by beta, and then alpha.
32
What are x-rays?
Electromagnetic radiation created when there is a change in the arrangement of the electrons in electron shells (QM).
33
What is neutron radiation?
Heavy particle with no charge emitted from nucleus by fission or bombardment by external particles. Very few radioisotopes are direct neutron emitters (often they emit gamma rays as well). Mass about equal to protons. Highly penetrating due to lack of charge (less than gamma, more than beta)
34
What are two devices that can detect radiation.
Geiger-Muller tube. Wilson cloud chamber.
35
Measurements of radiation.
Dosimetry: Measurement of radiation and the study of its effects on living organisms. Several units are used to determine radiation. Becquerel (Bq): Measurement of activity of a source. Not useful for effects on organisms. 1Bq=1emission per second. Currie (Ci): Amount of emitted particles given off by 1 gram of radium which is 3.7x10^10 emissions per second. Still not useful for biological effects. Absorbed dose. Amount of energy deposited by a source per kilogram of exposed tissue. 1J to 1kg of tissue is 1 Gray (1Gy). Depends a) on type of tissue (bone, organs, flesh, etc), b) number of particles per second hitting organism, and c) energy per particle. 1Gy=1J/kg=100Rads
36
Quality factor.
A number assigned to each type of radiation to describe its biological effects (approximate). x-rays, gamma rays, beta particles: 1. Thermal neutrons: 2. Fast neutrons: 10. Alpha particles: 20. (dangerous inside body).
37
Dose equivalent.
Sievert (Sv). Dose equivalent (sv) = absorbed dose (Gy) * quality factor (Q).
38
How many millisieverts can workers and the public experience?
Worker: 100mSv over 5 years, and 50mSv per year. Public: 1mSv per year.
39
What is considered by most people to be the primary effect of radiation?
Cancer.
40
What are stochastic health effects?
Associated with long-term chronic exposure. Increased levels of exposure make this health effect more likely to occur, but does not influence type or severity. Cancer.
41
What are non-stochastic health effects?
Appear in exposure to high levels of radiation and become more severe as exposure increases. Short term high level exposure is referred to as acute exposure.
42
How many millisieverts cause a detectable change in blood?
25mSv
43
How many sieverts cause immediate harmful effect?
Doses near 1Sv
44
What are some signs of radiation sickness?
Caused by doses over 1Sv: Nausea, vomiting, headache, fever, flu-like symptoms.
45
Does a nucleus have equal mass to its separated nucleons?
No, the nucleons have more.
46
Mass defect equation
delta m = parent mass - (daughter masses + ejected particle mass)
47
How does fission work?
Adding a free neutron to an atom (such as U-235) which splits it into other atoms, other neutrons, and releases energy.
48
Steps of fission?
Slow moving neutron shot at and captured by nucleus. Nucleus becomes unstable and splits. Two more fast moving nuclei form and are released. A large amount of energy is released.
49
Typical energy from fission of a U-235 atom?
200MeV.
50
Ideal fission of U-235?
U235+N -> Ba141+Kr92+3N This is the ideal reaction.
51
How does fusion work?
Atoms are fused together, releasing energy and forming a new nucleus and releasing other subatomic particles. Usually deuterium and tritium are fused into hydrogen, releasing a neutron.
52
Does fission of U-235 or fusion of deuterium and tritium release more energy?
For single reactions, fission will release more energy. However, fusion requires significantly less mass.
53
What is the problem with fusion?
It takes a lot of energy to start it. This is because of F=kq1q2 / d^2, meaning that it takes huge amounts of energy to move the nuclei close enough to each other to fuse.
54
What is the nuclear fuel cycle?
Mining, milling (yellow cake, getting uranium from rocks), conversion, enrichment (centrifuge), fuel fabrication, nuclear reactor, interim storage. After interim storage, it either goes to final disposition, or spent fuel processing (into Uranium to be enriched again, or plutonium (fabricated into fuel).
55
What are CANDU reactors?
CANadian Deuterium Uranium These reactors do not need enriched Uranium, and can use Uranium that has other materials such as Thorium or Plutonium mixed in.
56
What is a PWR?
Pressurized Water Reactor. Pressurizing water allows for water temps up to 320C. There are isolated loops of water, one is heated by the reactor. The other is heated by the pressurized water loop, turned into steam to spin a turbine, before being condensed and put back into the cycle.
57
What is a boiling water reactor?
Water touches nuclear fuel, cooling it and moving a turbine.
58
What is a liquid metal fast breeder reactor?
Reactor core of U235 and U238 blanketed in liquid sodium. Liquid sodium cool the reactor. Intermediate liquid sodium cooling loop. Water and steam loop to turbine. Makes power, and weapons grade fuel.
59
Liquid Fluorine Thorium Reactor.
LFTR ("lifter") makes energy by using liquid nuclear fuel, rather than solid fuel. A coolant is also used that is liquid at atmospheric pressure. There is no worry of meltdowns, as the Thorium is already liquid. A freeze plug will automatically drain it if it becomes too hot.
60
How are fast neutrons from fission allowed to cause other nuclei to undergo fission?
A moderator is used to slow down the neutrons.
61
What is a sustained fission reaction?
Fission that releases neutrons that cause other nuclei to also release neutrons.
62
How much U235 is there in normal Uranium?
About 0.7%.
63
What do control rods do?
They absorb neutrons, preventing the chain reaction of fission.
64
What is critical mass?
The mass of fissionable material that will produce a nuclear explosion. (sustainable nuclear reaction).
65
What is thermal neutron capture and activation?
Sometimes a nucleus will absorb a neutron, exciting the nucleus, emitting gamma rays, an unstable nucleus, releasing a beta particle, and leaving an excited nucleus. For example, U-235 may become Np-236 + beta particle
66
What is the IAIA:
Sets minimum standards for nuclear safety. An international organization.
67
What does Canada follow for nuclear safety?
CNA, monitored and governed by CNSC.
68
What three factors are critical to nuclear safety?
Limit TIME, increase DISTANCE, and increase SHIELDING.
69
How long did it take for the Trinity bomb to detonate?
8 millionths of a second. 0.000008s.
70
How do nuclear (fission) bombs work?
Two or more subcritical masses of fissionable material are brought together very rapidly. This produces devastating destruction and radioactive contamination.
71
How did the Little Boy work?
A gun was used to fire a subcritical mass into another subcritical mass (U235) creating a supercritical mass.
72
How did the Fat Man work?
A shell consisting of, conventional explosives, U-238, a hollow plutonium sphere, and a polonium beryllium agitator. The conventional explosives detonate, crushing the insides into a supercritical mass.
73
What are thermonuclear bombs?
Bombs that use fusion.
74
Failures in nuclear energy.
Three Mile Island: Failed relief value (problems known, ignored). No injuries or adverse health effects (directly attributed, other sources possible). Some radioactive gas released, but no more than background levels. Chernobyl: Safety turned off for a test. To conduct test, reactor fell to 25%. Failed and it went to 1%. In an attempt to bring it up, a power surge occurred (emergency shutdown failed, since it was off). Graphite at the bottom of control rods (defect, Soviet Union did not notify them) combusted. <50 deaths with 2000 expected. Fukushima: Tsunami took out backup generators used to cool rods and there wasn't enough water to keep the rods from melting. This was preventable as they were warned to move backup generators out of a basement (which flooded).
75
What is a meltdown?
Solid fuel heats up and liquefies (5000C).
76
What is "China Syndrome".
Melted fuel will continue to melt through containment, then floor, then through the Earth's crust.
77
How much energy did Trinity produce?
100TJ
78
How much energy did Little Boy produce?
63TJ
79
How much energy did Fat Man produce?
88TJ
80
Three interpretations of of Quantium Mechanics.
Copenhagen: Only the probability of some things can be predicted. Many Worlds: All possible outcomes exist as other worlds, rather than a collapse into one outcome. Pilot Wave Theory/Bohmian Mechanics: There are hidden variables affecting the outcome that we do not know.
81
Michelson-Morley experiment has what postulates?
This experiment attempted to measure the speed of the Earth, assuming that lights speed was constant through the 'ether' of space. It found that there was no difference in the motion of light when it traveled in different directions relative to Earth's travel. Postulate 1: All the laws of nature are the same in all uniformly moving reference frames. Postulate 2: Speed of light is a constant, independent of the motion of the light source or the observer.
82
Why are electron microscopes so much more powerful?
Electrons have far shorter wavelengths than visible light does.
83
Three interpretations of of Quantum Mechanics.
Copenhagen: Only the probability of some things can be predicted. Many Worlds: All possible outcomes exist as other worlds, rather than a collapse into one outcome. Pilot Wave Theory/Bohmian Mechanics: There are hidden variables affecting the outcome that we do not know.

Physics 30 (6 decks)

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