Particles and Waves Flashcards
(96 cards)
1
Q
What evidence is there for antimatter?
A
Positrons discovered ocurring naturally in cosmic rays.
2
Q
What is the Standard Model?
A
The Standard Model explains how the basic building blocks of matter interact, governed by four fundamental forces.
3
Q
What is a fundamental particle?
A
A fundamental particle is one that cannot be broken down into any sub particles.
4
Q
What is a Fermion?
A
It is a matter particle.
5
Q
What are the two types of Fermions?
A
Quark
and
Lepton
6
Q
What are the names of the 6 types of Quarks?
A
- Up
- Down
- Charm
- Strange
- Top
- Bottom
7
Q
What are the names of the 6 types of Leptons?
A
- Electron
- Electron neutrino
- Muon
- Muon neutrino
- Tau
- Tau Neutrino
8
Q
How does an antimatter particle compare with a matter particle?
A
Antimatter particle has similar properties to the matter particle but equal and opposite charge.
9
Q
What is meant by a Hadron?
A
Particles made from quarks
10
Q
What is meant by a Baryon?
A
Baryons are made from 3 quarks
11
Q
What is meant by a Meson?
A
Mesons are made from 2 quarks.
They always consist of a quark and an antiquark pair.
12
Q
Give an example of a Baryon.
A
Proton
Neutron
13
Q
What is a Boson?
A
Bosons are force carrying particles.
14
Q
Name the four Bosons.
A
- Photons
- W and Z Bosons
- Gluons
- Gravitons
15
Q
What force is carried by a photon?
A
Electromagnetic Force
16
Q
What force is carried by W and Z bosons?
A
Weak force
17
Q
What force is carried by a Gluon?
A
Strong force
18
Q
What force is carried by a Graviton?
A
Gravity force
19
Q
A proton is made up of two up quarks and a down quark. The up quarks are both positively charged. Why does the proton not get torn apart?
A
Gluons carry the strong force to hold the quarks together. This strong force is greater than the force of repulsion between the particles.
20
Q
What is beta (minus) decay?
A
Beta (minus) decay is when a neutron decays into a proton releasing an electron and an antineutrino.
21
Q
What did beta decay provide the first evidence for?
A
The existence of neutrinos.
22
Q
Why were neutrinos suggested as an extra particle produced as a result of beta decay?
A
When beta decay occurs momentum and energy should be conserved. This was not happening if only the proton and beta particle were considered. There had to be another particle that carried the rest of the energy away.
23
Q
In physics what is meant by a field?
A
It is the region where an object experiences a force.
24
Q
What is the definition for electric field strength?
A
The electric force per unit charge acting at a point in the field.
25
What is the definition for a potential difference of 1 Volt?
There is a potential difference of 1 Volt between two points if I joule of energy is required to move 1 coulomb of charge between the two points.
26
What will a stationary charge create?
An electric field
27
What will a moving charge create?
1. An electric field
2. Magnetic field
28
What will a moving charge experience in a magnetic field?
A force
29
What are the fingers representing in the right hand rule?
1. First Finger - Field (Magnetic field)
2. SeCond finger - Current
3. THumb - Thrust (Movement)
30
What represents a magnetic field coming 'out of the page'?
A dot
31
What represents a magnetic field going 'into the page'?
A cross
32
Explain how a particle accelerator works.
1. Acceleration of charged particles - use an **electric field** which causes particles to experience a force and accelerates them.
2. Deflection of charged particles - **magnetic fields** are used to chage the direction of the moving charged particles.
3. Collision of charged particles - against a fixed target or between two beams of particles.
33
Does a particle accelerator use a.c. or d.c. to create the electric field?
Explain why.
a.c.
This is because the electric field must change direction every time a particle completes a half circle (Dee) to keep the accelerating potential in the correct direction for the particles motion.
34
What information do you get from a chemical symbol, such as the one shown below?
**Top number** = Mass Number = number of protons and neutrons in the nucleus.
**Bottom Number** = Atomic Number = number of protons in the nucleus.
The letters are the chemical symbol which can be found on the periodic table.
35
If an unstable nucleus undergoes alpha decay what is given out and what is the effect on the mass number and the atomic number?
An alpha particle is a helium nucleus.
**Mass Number -** This means that the product mass number + the mass number of a helium nucleus = mass number of the original unstable nucleus.
**Atomic Number** - This means that the product atomic number + the atomic number of a helium nucleus = atomic number of the original unstable nucleus.
36
If an unstable nucleus undergoes beta decay what is given out and what is the effect on the mass number and the atomic number?
An electron from the nucleus is given out along with an antineutrino.
The mass number of the product remains the same and the atomic number increases by one.
37
What is meant by **fission**?
Fission is when a nucleus of a large mass number splits into two or more nuclei of smaller mass numbers.
38
What is meant by fusion?
Fusion is when two small mass number nuclei combine to form a nucleus of a larger mass number.
39
Give **one** advantage of producing electricity by nuclear fusion.
* Abundant fuel supply (Deuterium can be extracted from sea water)
* Safe (Small amounts of fuel, if reaction is unchecked it results in it stopping)
* Clean (No combustion so no air pollution)
* Less nuclear waste (waste is not high level weapons grade, needs stored for about 100 years)
* Efficient (1kg fusion fuel gives same energy as 10 million kg of fossil fuels)
40
What 2 conditions are required for nuclear fusion?
* High Temperatures
* High Pressure
41
In a fusion reactor why are the high temperatures required a problem?
High temperature required to give the hydrogen atoms enough energy to overcome the electrical repulsion between the protons. This is difficult to contain as all materials would vaporise at this temperature.
42
Containment and cooling are issues associated with a nuclear fusion reactor. Why?
Temperature of the reaction is so high most materials will vaporise. So a magnetic field can be used to suspend the plasma away from the sides of the container.
This requires strong magnetic fields produced by superconducting coils. These only work at cery low temperatures so need good cooling systems.
43
What is the photoelectric effect?
The photoelectric effect is when electromagnetic radiation is directed at a metal surface and ejects electrons from the surface.
44
When will a gold leaf electroscope discharge?
* It must be negatively charged
* It must have a zinc plate
* Ultraviolet light of a high enough frequency must be shone on the plate
45
Why does the photoelectric effect give evidence for light to be considered as a particle?
* Photoelectric effect cannot be explained if light is thought of as a wave or any light would cause photoemission if it shone on the surface long enough to deliver enough energy to the electrons..
* If light is considered as small bursts of energy carried by particles called photons then the photoelectric effect can be explained.
46
What is the threshold frequency?
The minimum frequency of light required to eject an electron from a metal surface.
47
What is the Work Function?
The minimum energy required to eject an electron from a metal surface.
48
If an incident photon is greater than the work function what happens to the rest of the photon's energy?
The electron that is ejected has the rest of the energy as kinetic energy.
49
In the photoelectric effect, if the frequency of the incident radiation is increased what happens?
The electrons ejected will have more kinetic energy, if the frequency is greater than the threshold frequency.
50
In the photoelectric effect, if the irradiance of the incident radiation is increased what will happen?
* No electrons will be ejected if the frequency of the incident radiation is below the threshold frequency.
* If the frequency is above the threshold frequency then more electrons will be ejected from the surface.
51
What can you say about electrons absorbing photons in the photoelectric effect?
* An electron can only absorb the energy from one photon
* The electron absorbs all the energy from the photon.
52
What is the frequency of a wave?
The number of waves per second.
53
What is the wavelength of a wave?
Wavelength is the distance from a point on one wave to the same point on the next wave.
54
What is the period of a wave?
The time it takes one wave to pass a point.
55
What is the amplitude of a wave?
The distace from the centre of a wave to the crest or trough.
56
What is the Law of Reflection?
Angle of incidence = Angle of reflection
57
What is meant by diffraction?
Diffraction is the bending of waves round an object.
58
What is a minima?
A point where destructive interference occurs.
59
What will increase the amount of diffraction?
* Longer wavelengths diffract more
* Narrower gaps cause more diffraction
60
What is a coherent source?
Waves that have a constant phase difference (and the same frequency, wavelength and velocity)
61
What is constructive intereference?
This occurs when two waves meet at a point in phase.
62
What is destructive interference?
Destructive interference occurs when two waves meet at a point exactly 180O out of phase.
63
What is the test for a wave?
If it can cause interference.
64
What is a maxima?
A point where constructive interference occurs.
65
How can you increase the spacing between the maxima?
* Increase the separation of the sources
* Increase the wavelength of the waves
* Increase the distance between the sources and screen/detector
66
What are the advantages of using a grating to produce an interference pattern instead of a double slit?
* Fringes are brighter
* Fringes are sharper
67
Using a grating how can you increase the spacing between the maxima?
* Use a grating with a smaller slit separation.
* Use a source with a greater wavelength of light
* Move the screen further away
68
If white light is shone through a grating what does the interference pattern look like?
* The central order maximum will be white
* At every other maxima a spectrum will be produced
69
What is refraction?
The change in speed of light (and wavelength) as it enters a different material, this can result in a change in direction.
70
What is meant by absolute refractive index?
It is the ratio of speed of light in a vacuum to the speed of light in the material.
71
A triangular prism can be used to split white light into a spectrum. Why does this occur?
Different frequencies/colours have different refractive indices.
72
What are the 4 differences in spectra produced by refraction (in a prism) and by a grating?
Prism Grating
One spectrum Many spectra
Produced by Refraction Produced by interference
Red light deviated least Red light deviated most
Spectrum is dim Spectrum is bright
73
What is the critical angle?
The angle of incidence that give an angle of refraction of ninety degrees.
74
When will total internal reflection occur?
* Incident light must arrive at the boundary at an angle greater than the critical angle
* Occurs when light tries to pass from an optically dense material to a less dense material
75
What is irradiance?
The power per unit area
76
What are the main features of the Bohr model of the atom?
1. Nucleus - central dense region containing most of the atoms mass. Contains positive protons and neutrons (no charge)
2. Electrons (negatively charged) are in discrete energy levels and do not radiate energy
3. When an electron makes a transition from one energy level to another a specific amount of energy is lost or gained
4. Each line in a spectrum is produced when an electron moves from one energy level to another.
77
What is the ground state?
This is the energy level with the least energy. It is the most negative energy level.
78
What is the ionisation level?
This is the energy needed by an electron to leave the atom altogether.
79
When is the energy of the ionisation level?
0 Joules
80
What type of spectrum is this?
Line emission spectrum
81
What type of spectrum is this?
Continuous spectrum
82
What type of spectrum is this?
Line absorption spectrum
83
If a spectral line is bright - what des this tell you?
More electrons are making that energy level transition producing more photons of light with the same frequency.
84
Are all photons produced by energy level transitions visible?
No, some frequencies of photons may be in in the ultraviolet or X-ray frequency
85
What do absorption lines in the Sun's spectrum show?
Evidence for the composition of the upper atmosphere of the Sun.
86
How are absorption lines in the Sun produced?
Photons of certain frequencies are absorbed by the gases in the outer atmosphere of the Sun.
87
Describe the field lines between two negative charges.
The field lines run towards the negative charges but no filed lines between them.
88
Describe the electric field around a positive charge.
Field lines away from the positive charge.
89
Describe the electric field around a negative charge.
Field lines towards negatively charged particle.
90
Describe the electric field between a positive charge and a negative charge.
Field lines run from positive towards negative.
91
Describe the field lines between two positive charges.
Field lines run away from the positive charges. No field lines between them.
92
Describe the field lines between parallel plates.
Field lines run from positive to negative plates.
93
In the equation E = mc2 , what does the m stand for?
The mass which is converted into energy, which is the difference in mass of the particles before the fission/fusion reaction and the mass after.
94
What is meant by irradiance?
The power per unit area
95
What is a point source?
This is a source where the light spreads evely in all directions
96
What is the effect of an electric field on a charged particle?
The particle will experience a force that causes an acceleration.
