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Higher Physics > Particles and waves > Flashcards

Particles and waves Flashcards

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1
Q

What is a transverse wave?

A

A transverse wave is a wave in which the motion of the medium is at right angles to the direction of the wave.

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2
Q

What is a longitudinal wave?

A

In a longitudinal wave, the motion of the medium is parallel to the direction of the wave. This means that the particles move left and right which in turn makes the other particles start to oscillate.

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3
Q

What do all waves have in common?

A

All waves transfer energy.

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4
Q

Give an example of a longitudinal wave.

A

Sound waves.

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5
Q

Give examples of transverse waves.

A

Radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, Gamma rays and water waves.

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6
Q

What is the wavelength of a wave?

A

The wavelength is the distance from a point on one wave to the same point on the next wave. It has the symbol λ

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7
Q

What is the definition of frequency?

A

Frequency is defined as the number of waves per second. It has the symbol f.
Frequency is measured in Hertz (Hz).

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8
Q

What happens to the frequency of a wave when it enters another medium?

A

The frequency doesn’t change.

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9
Q

What is the period of a wave?

A

The period of a wave is the time it takes one wave to pass a point. It has the symbol T. The time period, T ,of a wave is measured in seconds. (s). The period of the wave is equal to 1 divided by the frequency.

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10
Q

What is the amplitude of a wave?

A

Amplitude is the distance from the centre of the wave to the crest or trough. The bigger the amplitude the more energy the wave carries. Amplitude is measured in metres. (m)

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11
Q

What is wave speed?

A

Wave speed is the distance that a wave can travel in one second. It has the symbol, v. Wave speed is measured in metres per second. (ms-1)

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12
Q

How can the wave speed be calculated?

A

Wave speed can be calculated using (depends on the information you are given). d = vt or v=fλ

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13
Q

What are the four properties of waves?

A

All waves exhibit four properties: reflection; refraction; diffraction and interference.

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14
Q

What is the main rule for reflection?

A

Angle of Incidence = Angle of Reflection

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15
Q

What is the definition of diffraction?

A

This is the effect observed when waves bend round an obstacle e.g. radio waves round a hill, water waves through a harbour wall etc.

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16
Q

What happens to the wave speed when diffraction occurs.

A

There is no change in wave speed, wavelength or frequency when diffraction occurs.

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17
Q

What effect does the size of the gap have on the amount a wave diffracts?

A

The narrower the gap the larger the diffraction effect.

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18
Q

How does the wavelength of a wave effect the amount it diffracts?

A

Longer wavelengths (lower frequencies) diffract more than shorter wavelengths (higher frequencies). This can explain why you can pick up a radio signal in the mountains but not a mobile phone signal. Radio waves are longer wavelengths than mobile phone signals so diffract more.

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19
Q

Name the six types of quarks.

A

Up, down, charm, strange, top, bottom.

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20
Q

What is the charge of an Up quark?

A

It has an electric charge of +2/3.

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21
Q

What is the charge of a Down quark?

A

It has an electric charge of -1/3.

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22
Q

What are the qualities of a Charm quark?

A

It has an electric charge of +2/3 and it has a larger mass than an Up quark.

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23
Q

What are the qualities of an Strange quark?

A

It has an electric charge of -1/3 and a larger mass than a Down quark.

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24
Q

What are the qualities of a Top quark?

A

It has an electric charge of +2/3 and a larger mass than a Charm quark.

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25
Q

What are the qualities of a Bottom quark

A

It has an electric charge of -1/3 and a larger mass than a strange quark.

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26
Q

Name the six types of leptons.

A

Electron, Electron Neutrino, Muon, Muon Neutrino, Tau and Tau Neutrino.

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27
Q

What are the qualities of antimatter particles?

A

Antimatter particles have similar properties to the matter particles but opposite and equal charge.

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28
Q

What is the definition of a Hadron?

A

Hadrons are particles made from quarks.

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29
Q

What is the definition of a Baryon?

A

Baryons are particles made of 3 quarks.

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30
Q

What are the two subgroups of Hadrons?

A

Hadrons can be split into two subgroups.

1) Baryons
2) Mesons

The group a particle is in depends on the fundamental particles that make it up.

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31
Q

What is the definition of a Meson?

A

Mesons are made up of 2 quarks. They always consist of a quark and an antiquark pair.

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32
Q

What is the definition of a Boson?

A

Bosons are force carrying particles. The types of bosons are photons, W and Z bosons, gluons and gravitons.

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33
Q

What is a fundamental particle?

A

A fundamental particle cannot be broken down into any sub particles.

34
Q

What is the definition of electric field strength?

A

The electric field strength at a point is the electric force per unit charge acting at a point in the field.
Or
The electric field strength is the electric force acting on 1 Coulomb of charge at a point in the field.

35
Q

What is the definition of a volt?

A

There is a potential difference of 1 volt between two points if 1 joule of energy is required to move 1 coulomb of charge between the two points, 1 V = 1 J/C.

36
Q

What is the formula for work done?

A 
W = QV
W = EK
37
Q

What is the photoelectric effect?

A

The photoelectric effect occurs when electromagnetic radiation is directed at a metal surface and ejects electrons from the metal.

38
Q

What is formula for the energy carried by a photon of light?

A

E =hf

39
Q

What is the Threshold Frequency?

A

The Threshold Frequency is the minimum frequency of light required to eject an electron from a metal surface.

40
Q

What is the Work Function?

A

The Work Function is the minimum energy required to eject an electron from a metal surface.

41
Q

What is the formula for the kinetic energy for an ejected electron?

A

Kinetic energy = Energy of photon – Work Function

EK = hf – hfo

42
Q

What is the formula for constructive interference?

A

path difference = mλ where m is an integer 0, 1, 2, 3

S2P - S1P = mλ

43
Q

What is the formula for destructive interference?

A

path difference = ( m + ½ )λ where m is an integer 0, 1, 2, 3
S2P - S1P = ( m + ½ )λ

44
Q

What is the formula linking the wavelength of the light, the order of the maxima and the angle of deviation, ϴ.

A

mλ = d sinϴ

45
Q

What two things do you have to remember about stationary and moving charges?

A

A stationary charge creates an electric field, whereas a moving charge also creates a magnetic field.

46
Q

What is the basic operation of a particle accelerator.

A

1) Acceleration of charged particles - Accelerators speed up charged particles by
creating large electric fields which attract or repel the particles.

2) Deflection of charged particles – Magnetic fields are used to change the direction
of the charged particles.

3) Collision of charged particles – Can be against a fixed target, or between two beams
of particles. Particle detectors are placed around the collision point to record and
reveal the particles that emerge from the collisions.

47
Q

When will a gold leaf electroscope discharge?

A

When it is negatively charged.
When it has a zinc plate.
When ultraviolet light is shone on the plate.

48
Q

What is the main thing to remember about the photoelectric effect.

A

The photoelectric effect cannot be explained if light is thought of as a wave. If light is considered as small bursts of energy carried by
particles called photons then it can be explained. Thus light can be considered as a wave or a particle.

49
Q

What is a coherent wave?

A

Waves which are coherent have the same frequency, wavelength and velocity and have a constant phase relationship.

50
Q

What is the definition of nuclear fission?

A

Nuclear fission is when a nucleus of a large mass number splits into two or
more nuclei of smaller mass numbers.

51
Q

What is the definition of nuclear fusion?

A

Nuclear fusion is when two small mass number nuclei combine to form a
nucleus of a larger mass number.

52
Q

What are the difficulties with nuclear fusion?

A

High Temperatures. A very high temperature gives the hydrogen atoms enough energy to overcome the electrical repulsion between the protons. This requires temperatures of about 100 million Kelvin (6 times hotter than the Sun!) At this temperature hydrogen is a plasma. (Plasma is a high energy state of matter where electrons are stripped from the atoms and are free to move about)

High Pressures. Pressure is required to squeeze the hydrogen atoms together. They must be within 1 x 10 -15 m to fuse.

Materials that we currently have would vaporise at the temperatures required.

An extensive cooling system is required to keep the superconducting magnets cool enough to provide the magnetic field required.

53
Q

What are the main things to remember about the photoelectric effect?

A

An electron can only absorb the energy from one photon.
When a photon is absorbed by an electron, the electron absorbs all of the photons energy and not just a part of it.
Kinetic energy of electron = Energy of photon – Work function.
If the irradiance (brightness) of the radiation is increased more electrons are ejected.
This is because more photons are hitting the plate. This only works if the photons
have enough energy to cause the photoelectric effect i.e energy above the work function/frequency above the threshold frequency, if they do not then nothing will happen.
If the frequency of radiation being used is increased then the kinetic energy of the ejected electrons increases.

54
Q

When does constructive interference occur?

A

Constructive interference occurs when two waves meet at a point exactly in phase.

55
Q

When does destructive interference occur?

A

Destructive interference occurs when two waves meet at a point exactly 180 degrees out of phase.

56
Q

What only shows the property of constructive/destructive interference?

A

Only waves show this property of interference. Therefore, interference is the test for a wave.

57
Q

What experiment can be used to show the interference of light.

A

The Young’s Double Slit Experiment.

58
Q

What can alter the spacing between maxima and minima.

A

Increasing the separation of the sources S1 and S2 decreases the spacing between the maxima and the minima.
Increasing the wavelength of the waves increases the distance between the maxima and minima.
Increasing your distance from the source to the screen increases the spacing between the maxima and minima.

59
Q

What is the formula for finding the slit separation in a diffraction grating?

A

d = 1/number of lines per metre

60
Q

What do you need to consider about the spacing between the maxima when carrying out calculations?

A

The smaller the slit separation the greater the angle of deviation between the maxima, seen as an increased distance between the maxima on the screen.
The greater the wavelength of light the greater the angle of deviation between the maxima, seen as an increased distance between the maxima on the screen.

61
Q

What happens when white light is shone through a grating?

A

If white light is shone onto a grating then the central order maxima will be white but at every other maxima a spectrum will be produced.

62
Q

What is the definition of refraction?

A

Refraction is the change in direction of light caused by a change in speed as light enters a different medium.

63
Q

What is the absolute refractive index of a material?

A

The Absolute Refractive Index of a material is the ratio of the speed of
light in a vacuum to the speed of light in the material.

64
Q

How can the absolute refractive index be measured.

A 
n = sin 𝜃1/sin 𝜃2
n = 𝜆1/𝜆2 
n = 𝑣1/𝑣2
n = refractive index (no units)
𝜃1= angle in air from normal
𝜃2= angle in material from normal
λ1 = wavelength in air in metres (m)
λ2 = wavelength in material in metres (m)
v1 = velocity of light in air in metres per second (m/s)
v2 = velocity of light in material in metres per second (m/s)
65
Q

How can a spectrum produced by a prism can be explained?

A

A spectrum produced by a prism can be explained by: The higher the frequency of light the greater the refractive index.

66
Q

What is the definition of the critical angle?

A

The critical angle is the angle of incidence that results in an angle of
refraction of 90 degrees to the normal.

67
Q

What is the formula for the critical angle?

A

sin θc = 1/n
n = refractive index (no units)
𝜃𝑐= the critical angle in degrees

68
Q

What is the definition of total internal reflection?

A

Total Internal Reflection occurs when light passes from an optically dense material to air. Total Internal reflection occurs when the incident light enters at an angle greater than the critical angle.

69
Q

What is the formula for irradiance?

A 
I = P/A
I = Irradiance in watts per square metre (W/m)
P = Power in watts (W)
A = Area in metres square
70
Q

What is the main thing to remember about irradiance and distance?

A

As the distance from a light source increases the irradiance decreases.

71
Q

What is the formula linking irradiance and distance?

A

I = k/d2 (This should be distance squared)

72
Q

What are the main points of the Bohr model of the atom?

A

The Bohr Model of the atom is based on the Rutherford model. It has the following ideas:
• Neutrons and protons occupy a dense central region called the nucleus
• Protons are positively charged
• Neutrons have no charge
• The nucleus is positively charged
• Electrons are negatively charged
• Electrons orbit the nucleus
• Atom is mainly space
• Electrons are restricted to particular energy levels (orbits)
• The further from the nucleus the electron orbits the more energy the electron must have to stay in that orbit.

73
Q

What is the definition of the ground state?

A

The ground state is the energy level with the least energy, it will be the most negative and is called E0.

74
Q

What is the definition of the ionisation level?

A

The ionisation level is the energy needed by an electron to leave the atom altogether.

75
Q

What happens when an electron gains energy?

A

When an electron gains energy it is said to be in an excited state and moves to a higher (less negative) level.

76
Q

What happens to an electron when it escapes an atom?

A

The electron is said to have zero energy when it has escaped the atom. 0J.

77
Q

What happens when an electron loses energy?

A

An electron can also lose energy, it moves to a lower energy level and gives out energy as a photon.
The electrons move between the energy levels by absorbing or emitting a photon of electromagnetic radiation with just the correct energy to match the gap between energy levels.
As a result only a few frequencies of light are emitted as there are a limited number of possible energy jumps or transitions.

78
Q

Which statement is correct:

  • The brighter a spectral line the more electrons are making that particular energy jump producing more photons of light with the same frequency.
  • The thinner a spectral line the more electrons are making that particular energy jump producing more photons of light with the same frequency.
  • The less bright a spectral line the more electrons are making that particular energy jump producing more photons of light with the same frequency.
A

The brighter a spectral line the more electrons are making that particular energy jump producing more photons of light with the same frequency.

79
Q

If the energy lost as an electron drops is large enough what frequency of light could be emitted?

A

If the energy jump is large enough a photon of ultraviolet or X-ray could be obtained.

80
Q

What can be said about absorption spectra?

A

The absorption lines in the spectrum are produced by photons of specific frequency being absorbed by gases. (Could be gases in an atmosphere/ vapour lamp etc).

81
Q

What can absorption spectra help to discover about the Sun?

A

The absorption lines in the sunlight spectrum provides evidence for the composition of the upper atmosphere of the Sun. The absorption lines in the Sun’s spectrum are produced by photons of specific frequency being absorbed by gases in the Sun’s atmosphere.

82
Q

Name the newly discovered Meson.

A

The Tylertron!

Higher Physics (3 decks)

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