Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A Level Physics Year 1 > Electromagnetic Radiation and Quantum Phenomena > Flashcards

Electromagnetic Radiation and Quantum Phenomena Flashcards

You may prefer our related Brainscape-certified flashcards:
Physics 101 flashcards AP® Physics flashcards
1
Q

What happens if you shine radiation of high enough frequency onto the surface of a metal?

A

It will emit electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

For most metals, what range is the frequency of radiation necessary for the metal to emit electrons?

A

In the UV range

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the photoelectric effect?

A

The emission of electrons from a metal when light of high enough frequency is shone on it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the electrons that are emitted from a metal called?

A

Photoelectrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Why does shining radiation of high enough frequency onto a metal surface make electrons be released?

A

Metals contain free electrons on the inside, which absorbs energy from the radiation, making it vibrate. If an electron absorbs enough energy, the bonds holding it to the metal will break and the electron is released

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the minimum frequency of radiation needed for a given metal to emit electrons called?

A

Threshold frequency

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

The photoelectrons are emitted with a variety of…. This value of maximum…. increases with….?

A

The photoelectrons are emitted with a variety of kinetic energies. This value of maximum kinetic energy increases with the frequency of the radiation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the intensity of radiation on a metal?

A

The amount of energy per second hitting an area of the metal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

For the photoelectric effect, what is unaffected by varying the intensity of radiation?

A

The maximum kinetic energies of the photoelectrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is proportional to the intensity of the radiation for the photoelectric effect?

A

The number of photoelectrons emitted per second

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Why can’t wave theory explain the photoelectric effect?

A

The energy of a wave is proportional to its intensity. Increasing the intensity of the waves should increase the energy of the electrons that are emitted from the metal, but this doesn’t happen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What does the photoelectric effect show about light?

A

That light can’t just act as a wave

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are the discrete packets of EM waves also known as?

A

Quanta

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Who discovered the discrete packets of EM waves?

A

Max Planck

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What did Einstein suggest about EM waves?

A

He suggested that waves can only exist in discrete packets that he called photons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the photon model, developed by Einstein, which can explain the photoelectric effect?

A

He saw these photons of light as having a particle-like interaction with an electron in the metal surface, where each photon transferred all its energy to one specific electron

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Why can’t visible light be used to demonstrate the photoelectric effect?

A

It’s not got a high enough frequency

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the work function?

A

The minimum amount of energy needed for an electron to escape a metals surface

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What does the energy have to be compared to the work function for an electron to be emitted?

A

Energy has to be greater than the work function

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What happens if the energy of a photon is less than the work function of the metal?

A

The electron will shake a bit then release it’s energy as a photon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the equation for the threshold frequency?

A

Threshold frequency = Work function / Planck’s constant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

How do solar cells use the photoelectric effect?

A

They convert light energy into electricity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is the energy transferred from EM radiation to an electron equal to?

A

The energy the electron absorbs from one photon, hf

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is the kinetic energy as the electron leaves the metal equal to?

A

hf (energy of photon) minus any other energy losses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Why do electrons emitted from metals have a range of different kinetic energies?

A

Because they all have different energy losses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is the minimum amount of energy an electron can lose equal to?

A

The work function

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What is the photoelectric equation?

A

hf = work function + max kinetic energy

hf = Φ + E k max 
hf = Φ + 0.5 m (Vmax)^2
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is the intensity of photons?

A

The number of photons per second on an area

29
Q

What effect on the kinetic energy of the electrons does increasing the intensity of photons?

A

Doesn’t have an effect

30
Q

Why does increasing the intensity not effect the kinetic energy of the electrons?

A

An electron can only absorb one photon at a time. Increasing the number hitting an area per second doesn’t change the energy of the photons, so each electron absorbs the same amount of energy

31
Q

What is the stopping potential?

A

The P.D needed to stop the fastest moving photoelectrons in the photoelectric effect

32
Q

What is the equation for stopping potential?

A

eVs = Ekmax

e = charge on electron
Vs = stopping potential
Ekmax = maximum kinetic energy
33
Q

What is the electron volt defined as?

A

The kinetic energy carried by an electron after it has been accelerated from rest through a potential difference of 1V

34
Q

What is 1eV equal to in joules?

A

1.6x10^-19 J

35
Q

What is the ground state?

A

The lowest energy level an electron can be in, given the value n=1

36
Q

What is meant by ‘an electron is excited’?

A

It is in a higher energy level than the ground state

37
Q

How do electrons move down an energy level?

A

By emitting a photon

38
Q

What is it called when an electron moves up an energy level?

A

Excitation

39
Q

What is ionisation?

A

When an electron reaches the top of the energy ladder (where n=∞) can permanently leave the atom

40
Q

What are the 2 ways an electron can be excited?

A

By a photon

By a particle

41
Q

How does an electron get excited by a photon?

A

A photon with exactly the correct amount of energy gives up all of its energy to the electron, causing the electron to travel up the energy ladder to a higher energy level

42
Q

How do you work out the photon energy causing excitation?

A

It’s the difference in energy of the 2 energy levels (E1 - E2)

43
Q

What happens to the remaining photon energy once an electron has been ionised?

A

It is transformed into kinetic energy of the escaping electron

44
Q

How does an electron get excited by a particle?

A

An incident particle can give up a fraction of its energy to the electron, causing it to travel up the energy ladder to a higher energy level

45
Q

What must the kinetic energy of the particle be greater than in order for excitation to take place/

A

Must be greater than or equal to E1-E2 (photon energy)

46
Q

What is the main difference between a particle causing excitation compared to a photon causing excitation?

A

A particle can excite more than one electron before losing all its energy, whereas the photon can only excite one electron

47
Q

What is the ionisation energy of an atom?

A

The amount of energy needed to remove an electron from the ground state atom

48
Q

How do fluorescent tubes work?

A

They contain mercury vapour, across which a high voltage is applied. This voltage accelerates fast-moving free electrons that ionise some of the mercury atoms, releasing more free electrons. When the flow of free electrons collides with the electrons of the mercury atom, the atomic mercury electrons are excited to a higher energy level. When these excited electrons return to ground state, they release energy be emitting photons in the UV range. A phosphorus coating on the inside of the tube absorbs these photons, exciting its electrons to higher energy levels. These electrons then travel down the energy levels, releasing their energy as lower energy photons of visible light

49
Q

What do you get if you split the light from a fluorescent tube with a prism of diffraction grating?

A

A line spectrum

50
Q

What is a line spectrum?

A

A pattern of lines produced by photons being emitted or absorbed by electrons moving between energy levels in an atom

51
Q

What is a line emission spectrum?

A

A spectrum of bright lines on a dark background corresponding to different wavelengths of light that have been emitted from a light source

52
Q

What do line spectra provide evidence for?

A

That the electrons in an atom exist in discrete energy levels

53
Q

Which has the longest wavelength, red or blue light?

A

Red

54
Q

What is a line absorption spectrum?

A

A light spectrum with dark lines corresponding to different wavelengths of light that have been absorbed

55
Q

What do you get if you split white light up with a prism?

A

A continuous spectrum

56
Q

Why do hot objects emit a continuous spectrum in the visible light and UV range?

A

Because they emit electromagnetic radiation at all wavelengths or colours

57
Q

What is a blackbody?

A

An object that absorbs all the light falling on it, reflecting none of it, hence, it appears black

58
Q

When do you get a line absorption spectrum?

A

When light with a continuous spectrum of energy passes through a cool gas

59
Q

Why do you get a line absorption spectrum when white light passes through a cool gas?

A

At low temperatures, most of the electrons will be in the ground state. Photons of the correct wavelength are absorbed by the electrons to excite them to higher energy levels. These wavelengths are then missing from the continuous spectrum when it comes out the other side of the gas

60
Q

How can you compare line absorption spectra with emission spectra?

A

For a particular gas, the black lines in the absorption spectra correspond to the bright lines in the emission spectra

61
Q

What is wave-particle duality?

A

All particles have wave and particle properties (and waves have wave and particle properties)

62
Q

What is the evidence for the electron having wave-like properties?

A

Electron diffraction and interference through a piece of graphite

63
Q

What is the evidence for the electron having particle-like features?

A

The deflection of electron beam when shone through a magnetic or electric field

64
Q

What is the evidence for light having wave-like properties?

A

Youngs Double Slit experiment

65
Q

What is the evidence for light having particle-like properties?

A

Photoelectric effect

66
Q

What is the equation for De Broglie wavelength?

A

Planck’s Constant / Momentum

h/p = h/mv

67
Q

How can electrons be used to investigate the spacing between atoms in a crystal?

A

An electron beam will diffract when the De Broglie wavelength of the electrons is roughly the same size as the spaces between the atoms

68
Q

Why do electron microscopes have a higher resolution than light microscopes?

A

A shorter wavelength gives smaller diffraction effects (diffraction effects blur detail on an image)

A Level Physics Year 1 (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions