Brainscape's Knowledge GenomeTM

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


See full index

Physics The Good One > quanta > Flashcards

quanta Flashcards

1
Q

What did Planck work on?

A

He looked at black body radiation. He theorised that radiation was emitted in discrete packets of energy. He found there was a link between energy and frequency.

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

What is a Quanta?

A

Discrete packets of energy.

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

E = hf

A

The equation which Planck made, he had to make the constant h = 6.63 x10^-34 for it to work.

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

What did Einstein theorise?

A

That concentrated packets of energy had particle-like properties and were called photons.

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

Photon

A

Concentrated discrete packets of energy which have particle-like properties.

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

What is the EM spectrum from a particle point of view?

A

Many photons with different levels of energy.

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

How much do photons weigh?

A

Weightless.

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

How can photons travel at the speed of light?

A

Because they’re weightless.

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

What letter represents the speed of light?

A

c.

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

How is the equation E = hc/λ formed?

A

Combining E = hf and c = fλ.

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

Electron volt

A

One electronvolt is the energy gained by an electron when it is accelerated through a p.d. of 1v (W = QV).

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

How to convert joules to eV

A

Divide by 1.6x10^-19.

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

How to convert eV to Joules

A

Multiply by 1.6x10^-19.

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

How to find Planck’s constant?

A

Set up a potential divider circuit with a parallel section with different coloured LEDs, an ammeter, and a voltmeter. Measure the voltage and record the wavelength (read from the packet). Plot a graph of V against 1/λ. The gradient equals Vλ. Substitute E = eV into E = hc/λ, input values and rearrange to get h.

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

Who worked out the photoelectric effect?

A

Einstein.

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

What is the photoelectric effect?

A

The emission of electrons from the surface of, generally, a metal in response to incident light.

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

What shows the photoelectric effect?

A

When a charge is given to an electroscope, they repel each other, so the gold leaf will lift and move away from the metal pole.

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

How can the charge of an electroscope be found?

A

The angle the gold leaf lifts to.

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

Why does the wave model not back up the photoelectric effect?

A

All the frequencies should combine energy to liberate the electrons.

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

How many photons can liberate a single electron?

A

ONE.

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

If wavelength increases…

A

Frequency decreases, therefore electrons have less kinetic energy, and eventually, none are liberated.

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

If wavelength decreases…

A

Frequency increases, therefore electrons have more kinetic energy.

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

If intensity increases…

A

More electrons are emitted but with the same kinetic energy. If it is below the threshold frequency, intensity has NO effect.

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

Electrons are trapped inside __________ and in order to escape it has to _________

A

Energy wells, absorb enough energy.

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

How does the material affect the energy well?

A

Different sizes, therefore different amounts of energy are needed to liberate the electrons.

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

Work function

A

The amount of energy needed for the electrons to escape their energy well.

27
Q

Which formula works out the work function

A

hf = Φ + E.K. max.

28
Q

If the electron is given just enough energy to release from the energy well, its kinetic energy equals 0, therefore…

A

Threshold frequency can be found by Φ/h.

29
Q

It doesn’t matter how many IR photons land on the metal… if

A

All of them are below the threshold frequency, no single electron will be liberated.

30
Q

Photoelectron

A

A liberated electron.

31
Q

Intensity is proportional to

A

Rate of emission of photoelectrons.

32
Q

Broglie

A

Said that for any particle that had momentum, it also has wavelength λ = h/p.

33
Q

Relativistic mass

A

As a particle gets closer to the speed of light, the mass tends to increase due to relativistic effects.

34
Q

The intensity of a wave at a point represents

A

The probability of a wave being there.

35
Q

The electrons have _____ different energy levels, but its energy is _______

A

Infinite, finite.

36
Q

How do you work out the energy changes of an atom?

A

Calculate the frequency and wavelength needed to give the energy to move up levels and equally how much is emitted when it falls back down levels.

37
Q

Emission spectra

A

Shows the certain wavelengths of photons which are given off by an element after it is excited and the electrons drop back down to their original energy levels and emit energy.

38
Q

Absorption spectra

A

Where certain frequencies of light are missing because they’re being absorbed by that element.

39
Q

Threshold frequency

A

The lowest frequency of light at which electrons are still released from a surface.

40
Q

Wave equation

A

v = fλ.

41
Q

What experiment determines the work function of different materials and the value of h?

A

Stopping voltage experiment.

42
Q

What does the graph from the stopping voltage experiment show?

A

Gradient = h, F0 (x-intercept) = threshold frequency, y-intercept = work function.

43
Q

What does the y-intercept from the stopping voltage experiment show?

A

The voltage needed to stop an electron being liberated by light of 0 frequency and so 0 energy (the work function).

44
Q

What axes are plotted from the stopping voltage experiment?

A

y = stopping voltage, x = frequency.

45
Q

What direction does current flow?

A

Positive to negative (out the small end).

46
Q

What direction do electrons form?

A

Negative to positive.

47
Q

If the p.d. in a stopping voltage experiment is increased, what happens?

A

Electrons are accelerated faster as they move in the same direction as the current.

48
Q

If the p.d. in a stopping voltage experiment is decreased, what happens?

A

The battery is more effective than the photoelectric effect; therefore, the electrons are slowed and start to move backwards.

49
Q

What is stopping voltage?

A

The voltage at which the battery becomes more powerful than the photoelectric effect and the electrons are slowed.

50
Q

Electric field

A

The electric force per unit charge.

51
Q

How does an electron gun create a beam of electrons?

A

A hot filament causes thermionic emission of electrons. The electrons are repelled away from the negative electrode and towards the positive electrode, causing an accelerating force. Collimation takes place as the electrons are forced through a small gap. There must be a vacuum.

52
Q

How are ions accelerated?

A

Electric fields exist between positive and negative electrodes, implying a force on the ions causing acceleration.

53
Q

Force = rate of change of

A

Momentum.

54
Q

Why are electrons only emitted above a threshold frequency?

A

Photon energy is proportional to frequency; therefore, photon energy must be greater than the work function to liberate an electron. All the energy must come from a single photon.

55
Q

Line spectra

A

Specific frequencies/wavelengths show the absorption/emission lines within a narrow line of wavelengths.

56
Q

How do line spectra provide evidence for the existence of energy levels in atoms?

A

Photons associated with particular energies show electron transitions up and down the discrete energy levels to provide the line spectra.

57
Q

Kinetic energy gained by accelerating electron through a potential difference =

A

eV.

58
Q

Why are only certain frequencies absorbed by atoms?

A

Electrons can only exist in discrete energy levels.

59
Q

Ground state

A

The lowest energy level where electrons are usually found.

60
Q

Energy delivered by photon (hf) =

A

Difference between the energy levels.

61
Q

How can electrons be excited?

A

If a photon is absorbed or if electrons are hit by other electrons.

62
Q

How is a photon emitted?

A

Electrons don’t remain in an excited state, so they de-excite and drop down to the ground state, emitting energy in the form of a photon.

63
Q

High frequency photon means…

A

The more energy levels it jumps up.

64
Q

Long wavelength photon means…

A

Less energy levels moved up.

Physics The Good One (16 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions