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Higher Physics > Unit 2 - Particles and Waves > Flashcards

Unit 2 - Particles and Waves Flashcards

1
Q

What are fundamental particles?

A

Fundamental particles are not composed of other particles. This means that fundamental particles cannot be ‘broken down’ into smaller particles.

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2
Q

What are fermions?

A

Matter particles (if a particle has mass then it must be a fermion). Quarks and Leptons.

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3
Q

What types of leptons are there?

A

Electrons, muons, tau and 3 neutrinos.

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4
Q

What are bosons?

A

Force mediating particles.
Gluon - strong force
W and Z bosons - weak nuclear force
Graviton - Gravitational force
Photon - Electromagnetic force

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5
Q

What are hadrons?

A

mesons and baryon.

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6
Q

What are mesons made of?

A

One quark and one antiquark.

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7
Q

What are baryons made of?

A

3 quarks OR 3 antiquarks.

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8
Q

What is proof of the antineutrino and therefore the neutrino?

A

Beta decay.

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9
Q

What is potential difference of two points in an electric field?

A

A measure of the work done (W) in moving a coulomb of charge (Q) between the two points.

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10
Q

Explain how a cyclotron accelerator works

A

Ions are injected at a point near the centre. An alternating potential difference between the ‘dee’ shaped electrodes accelerates the particles. A magnetic field causes the particles to move in a circular path. When the particle crosses from one ‘dee’ to another it accelerates. After each acceleration, the particle moves to a slightly larger orbit. When it reaches the outer edge of the cyclotron the particle beam is extracted and used in other experiments.

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11
Q

Explain how a linear accelerator (LINAC) works.

A

Charged particles are accelerated in a vacuum pipe through a series of electrodes by an alternating voltage. The beam of particles is then directed at a target or into a synchrotron.

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12
Q

Explain how a synchrotron works.

A

This is similar to a linear accelerator, bent into a ring so the charged particles can be given more energy each time they go round. Electromagnets keep the particles in a curved path. As the speed increases, the magnetic field strength is increased. As the speed increases and relativistic effect cause the mass of the particles to increase, a larger force is needed to accelerate them and keep them in a circular path.

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13
Q

What is meant by the term nuclear fusion?

A

Two small nuclei combine to form a larger nucleus.

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14
Q

Why is energy released in nuclear reactions?

A

Some mass is lost and converted to energy.

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15
Q

Why do you need magnetic fields to contain plasma inside a fusion reactor?

A

Plasma would cool down if it came too close to the sides OR plasma would melt the sides of the reactor.

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16
Q

What is threshold frequency (f₀)?

A

Threshold frequency is the minimum frequency of a photon required to cause photoemission (an electron to be ejected)

17
Q

What is work functions (hf₀)?

A

Work function is the minimum energy required to cause photoemission (an electron to be ejected)

18
Q

What is constructive interference?

A

When waves meet in phase

19
Q

What is destructive interference?

A

When waves meet exactly (180°) out of phase

20
Q

What is absolute refractive index (n)?

A

Absolute refractive index of a medium is the ratio of the speed of light in a vacuum to the speed of light in
a medium.

21
Q

What is the critical angle?

A

Critical angle is the angle of incidence that causes the angle of refraction to be 90°

22
Q

What is irradiance (I)?

A

Irradiance is the power per unit area (incident on a surface).

23
Q

Describe what 6Wm^-2 means.

A

If there is an irradiance of 6 W m-2 at a surface, this means that 6 W of power is incident on 1 square metre
of surface.

24
Q

Explain why the photoelectric effect provides evidence for the particle nature of light

A

Each photon contains a fixed amount of energy. If light was a wave then the photoelectric effect would occur regardless of the frequency of the light, it would just take longer for electrons to absorb the energy required to be ejected.

25
Q

What happens to the remaining energy in not used to eject electrons in photoelectric emission?

A

It is converted to kinetic energy.

26
Q

Explain the photoelectric effect with a gold leaf electroscope.

A

A zin plate that’s negatively charged so covered with negative electrons causes the gold leaf to be repelled by the stem. Ultraviolet light is shone onto the plate which has efficient energy to eject electrons (the photons have energy higher than the work function of zinc). Electrons on zinc escape to air and are replaced by electrons from stem and gold leaf, meaning the gold leaf is not reflected from stem so falls. Higher irradiance of ultra-violet means gold leaf falls faster because more ultra-violet photons strike zinc per second.
NOTE
White light doesn’t do anything as energy isn’t high enough. Ultra-violet on tin plate does not fall, higher work function. If electroscope positively-charged, gold leaf does not fall because stem and gold leaf lack electrons so can’t replace electrons emitted from metal plate.

27
Q

What does coherent mean?

A

When two waves have a constant phase relationship. Also means the two sources have the same frequency and speed.

28
Q

How do you calculate how many lines the grating has if it has 100 liens per millimetre?

A

100 lines in a mm
= 100 000 in a mm
d = 1/100 000
= 1x10^-5

29
Q

What wavelength is blue green and red?

A

Blue = 450nm
Green = 550nm
Red = 650nm

30
Q

What is refraction?

A

Refraction is the changing of speed of light as it passes from one medium to another.

31
Q

When does total internal refraction occur?

A

When the angle of incidence is greater than the critical angle.

32
Q

What is a point source?

A

A point source of light emits light evenly in all directions.

33
Q

What is the energy level closest to the nucleus called?

A

Ground level.

34
Q

What are the energy levels farther from the nucleus called?

A

Excited energy levels.

35
Q

When does an electron reach the ionisation level?

A

When it reaches a distance so far away from the nucleus that the electron can escape from the atom. The atom is said to be in an ionisation state.

36
Q

Out of E3, E2, E1 and E0, what two states create the highest and lowest frequency?

A

Highest frequency (short wavelength) - E3-E0
Lowest frequency (long wavelength) - E3-E2

37
Q

Explain in terms of wave show a maxima is produced.

A

Waves meet in phase.

38
Q
A

Higher Physics (4 decks)

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