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Physics UNIT 3+4 > UNIT 4 > Flashcards

UNIT 4 Flashcards

1
Q

What is a pion

A

a subatomic particle produced in the atmosphere as a result of the collision of cosmic ray protons with nitrogen and oxygen atoms

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2
Q

What is a muon

A

an elementary particle similar to the electron but with a greater mass; it is the product of the decay of pions

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3
Q

What is the theory of special relativity

A

a theory that all the motion must be defined relative to a frame of reference; it consists of two principal postulates. It explains how space and time are linked fro objects moving at a constant speed in a straight line, and forms part of the basis of modern physics.

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4
Q

What is a frame of reference

A

an arbitrary set of axes with reference to which the position or motion of something is described or physical laws are formulated

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5
Q

What is relative motion

A

the motion of an object with regard to some other moving object is not calculated relative to the earth, but it’s the velocity of the object in reference to other moving objects as if it were in a static state.

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6
Q

What is inertial frame of reference

A

a non-accelerating frame of reference in which Newton’s Law of motions hold

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7
Q

What are the two Postulates of special relativity

A
  • The laws of physics are the same in all inertial frames of reference
  • The speed of light in a vacuum has the same value, c, in all inertial frames of reference
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8
Q

What is the definition of relativity of simultaneity

A

events that are simultaneous in one frame of reference are not necessarily simultaneous in another frame of reference, even if both frames are inertial

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9
Q

What is proper time

A

a time between two event measured by and observer at rest to the events. ONE clock is needed

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10
Q

What is relativistic time

A

a time between two events measured by an observer moving with respect of the events, dilated time. TWO clocks are needed

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11
Q

What is length contraction

A

a shorter measurement made by an observer moving relative to the object in the direction of the length being measured

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12
Q

What is proper length

A

the length as measured by an observer at rest with respect to the object

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13
Q

What is relativistic length

A

the length as measured by an observer moving with respect to the object in the direction of motion

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14
Q

What is relativistic momentum

A

the momentum of an object as measured by an observer moving relative to the object

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15
Q

What does the universal speed limit mean

A

The amount of momentum required to travel faster than the speed of light is to large to achieve

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16
Q

What is the twin paradox

A

If two twins existed and one was to go to space at an average speed of 0.8 c, the twin in space will have aged 30 years while the twin on earth will have 50 years

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17
Q

What is the resolution to the twin paradox

A

The twin on earth is correct is saying the spec twin has aged less. Special relativity will only apply to objects that are in uniform motion, the spec twin will have had to accelerate and decelerate in his journey making the length of his trip contracted whereas the Earth twin will measure the proper length.

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18
Q

What is the pole and the barn paradox

A
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19
Q

Definition of black body

A

an object that absorbs all radiation falling on it, at all wavelengths; it is the perfect absorber and emitter of radiation

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20
Q

Definition of black body radiation

A

the radiation emitted by a black body from the conversion of thermal energy, and which has a characteristic frequency distribution that depends on the temperature

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21
Q

What are the features of Wien’s Law

A
  • All black bodies at the same temperature will produce the same spectrum
  • The hotter the object the more radiation emitted
  • The higher the temperature the shorter the wavelength
  • The visible rainbow is only a small region on the whole emission spectrum, which also includes IR and UV
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22
Q

Explain Young’s double slit experiment

A

this experiment demonstrates the wave nature of light by allowing two coherent beams of light to overlap and create and interference pattern

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23
Q

What is an electromagnetic wave

A

a wave produced by an oscillating electric charge that radiates out at the speed of light as mutually perpendicular electric and magnetic fields

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24
Q

What is a quanta

A

the smallest discrete packets of energy of electromagnetic waves, also later known as photons

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25
Q

What is Plancks constant

A

a fundamental constant sued in quantum mechanics called quanta, that relates frequency to energy

26
Q

What is the photoelectric effect

A

the emission of electrons (or other free carriers) when light shines on a material

27
Q

What is a photon

A

a quantum of all forms of electromagnetic radiation

28
Q

Define momentum

A

the product of an objects mass and its velocity; it is a vector quantity and is conserved in interactions

29
Q

What is Rutherfords model

A

a small central positively charged nucleus with negatively charged electrons orbiting around it

30
Q

Limitations of Rutherfords model

A
  • the failure to account for the stability of the atom
  • the failure to account for emission lines in the hydrogen spectrum
31
Q

Explain the Bohr model

A

electrons orbit the nucleus in particular circular orbits called stationary states with foxed angular momentum and energy, their distance from the nucleus (their radius) being proportional to their energy. When an electron moves between these stationary states, it is accompanied by the emission or absorption of a photon

32
Q

Name the three Bohrs postulates (STA)

A
  • electrons in an atom exist in stationary states
  • the transition between stationary states absorbs or emits electromagnetic radiation
  • Angular momentum of a stationary electron is quantised
33
Q

What is the principal quantum number, n

A

is a discrete variable assigned to each electron in an atom to describe the energy level of the electron, with higher numbers representing higher potential energy (further from the nucleus)

34
Q

What is wave-particle duality

A

every particle or quantum entity may be partly described in terms not only of particles but also of waves

35
Q

What is an orbital

A

region of space around the nucleus of an atom where an electron is likely to be found

36
Q

What type of spectrum is emitted from a hydrogen-filled discharge tube?

A

Line spectrum

37
Q

What is the continuous spectrum

A

contains all wavelengths of light in a certain range

38
Q

In order to excite an atom, a photon must have energy:

A

equal to energy difference between two shells

39
Q

Definition of Standard model

A

a theory describing three of the four known fundamental forces in the universe, as well as classifying all known elementary particles

40
Q

Definition of elementary particles

A

a particle with no substructure, and thus not composed of other particles

41
Q

Definition of Higgs Boson

A

an elementary particle in the Standard model that acts as a ‘force carrier’ for the Higgs field- a field that pervades the universe and is responsible for giving certain elementary particles mass. It is similar to the way a photon is a force carrier for the electromagnetic field

42
Q

Definition of antiparticle of matter

A

a particle that has the same mass and the opposite charge and/or spin as a corresponding particle; for example, positron and electron

43
Q

Definition of an anti proton

A

the anti-particle of the proton, with an electric charge of -1e. It is relatively stable but it is typically short-lived because any collision with a proton causes both particles to be annihilated in a burst of energy

44
Q

Definition of quark

A

subatomic particles governed by the strong nuclear force that constitute hadrons; there are six quarks in the standard model

45
Q

Definition of anti quark

A

a particle with the same mass and opposite charge to the corresponding quark; for example, a strange quark and antistrange quark are said to be antiparticles

46
Q

Definition of hadron

A

particle composed of quarks and gluons

47
Q

Definition of gluons

A

the fundamental exchange particle that operates between quarks and hence underlies. the strong nuclear force between nucleons in the nucleus

48
Q

Definition of meson

A

subatomic particle composed of one quark and one antiquark, held together by the strong nuclear force

49
Q

Definition of baryon

A

composite subatomic particle made up of three quarks (or three antiquarks) held together by the strong nuclear force

50
Q

Definition of lepton

A

a class of elementary particles that respond only to the weak force and the gravitational force. They can carry one unit of electric charge or are neutral, and those that are charged experience electromagnetic force. There are six leptons in the standard model

51
Q

Definition of fundamental forces

A

those that act between bodies of matter and are mediated by one or more particles. In order from strongest to weakest: the strong nuclear force, the electromagnetic force, the weak force, the gravitational force.

52
Q

Describe strong nuclear force and mediating particle

A

a force used to hold together the nucleus
binds quarks together to make subatomic particles such as protons and neutrons and underlies interactions between all particles containing quarks, mediated by gluons.

53
Q

Describe the electromagnetic force and mediating particle

A

hold electrons in the atoms and bind matter together, mediated by photons

54
Q

Describe the weak force and mediating particle

A

responsible for the radioactive decay of atoms, mediated by W and Z bosons

55
Q

Describe the gravitational force

A

holds the universe together

56
Q

Define mediating particle

A

name for gauge bosons, which govern the interaction of the four fundamental forces; carrier or exchange particles.

57
Q

What is a baryon number

A

a quantum number defined by…., it is strictly conserved and additive. It is representative of the difference between the number of quarks and antiquarks

58
Q

What is conservation of baryon number

A

an interaction baryon number is conserved

59
Q

What is conservation of lepton number

A

an interaction lepton number is conserved

60
Q

What is conservation of lepton number

A

quantum number representing the difference between number of leptons and anitleptons in an elementary particle reaction

Physics UNIT 3+4 (2 decks)

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