Brainscape's Knowledge GenomeTM

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


See full index

A-Level PHYSICS Edexcel > quantum > Flashcards

quantum 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 theyre 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/ lambda 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 bu 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 plancks constant?

A
  • set up a potential divider circuit with a paralell section with different coloured LEDs, an ammeter and a voltmeter
  • measure the voltage and record the wavelength (read from packet)
  • plot a graph of v agaisnt 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 too

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

why does the wave model no backup 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 decrease

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 increased 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
How does the material effect the energy well?
different sizes therefore different amounts of energy are needed to liberate the electrons
26
work function
the amount of energy needed for the electrons to escape their energy well
27
which formula works out the work function
hf = Φ + E.K. max
28
if the electron is given just enough energy to release from the energy well its kinetic energy equals 0 therefore....
threshold frequency can be found by Φ/h
29
it doesn't matter how many IR photons land on the metal... if
all of them are below the freshold frequency no single electron will be liberated
30
photoelectron
a liberated electron
31
intensity is proportional to
rate of emmision of photoelectrons
32
Broglie
said that for any particle that had momentum it also has wavelength λ = h/p
33
relativistic mass
as a particle gets closer to the speed of light the mass tends to increase due to relativistic effects
34
The intensity of a wave at a point represents
the probability of a wave being there
35
the electrons have _____ different energy levels by its energy is _______
infinite | finite
36
how do you work out the energy changes of an atom?
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
emission spectra
shows the certain wavelengths of photons which are given off by an element after it is excited and the electrons drop back down to there original energy levels ad emit energy
38
absorption spectra
where certain frequencies of light are missing because they're being absorbed by that element
39
Threshold frequency
the lowest frequency of light at which electrons are still released from a surface
40
wave equation
v = fλ
41
what experiment determines the work function of different materials and the value of h?
stopping voltage experiment
42
What does the graph from the stopping voltage experiment show?
gradient = h F0 (x intercept) = threshold frequency y intercept = work function
43
What does the y intercept from the stopping voltage experiment show?
the voltage needed to stop an electron being liberated by light of 0 frequency and so 0 energy (the work function)
44
What axises are plotted from the stopping voltage experiment?
``` y = stopping voltage x = frequency ```
45
what direction does current flow?
positive to negative (out the small end)
46
what direction do electrons from?
negative to positive
47
if the p.d. in a stopping voltage experiment is increased what happens?
electrons are accelerated faster as they move in the same direction as the current
48
if the pd. in a stopping voltage experiment is decreased what happens?
the battery is more effective than the photoelctric effect therefore the electrons are slowed and start to move backwards.
49
what is stopping voltage?
the voltage at which the battery becomes more powerful than the photoelectric effect and the electrons are slowed
50
electric field
as the electric force per unit charge.
51
How how does an electron gun create a beam of electrons?
A hot filament causes thermionic emmision of electrons. the electrons at repelled away from the 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
How are ions accelerated
Electeic fields exist between positive and negative electrodes implying a force on the the ions causing acceleration
53
Force = rate of change of
Momentum
54
Why are electrons only emitted about a threshold frequency?
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 electron.
55
Line spectra
Specific frequencies/wavelengths show the absorbtion/ emmision lines within a narrow line of wavelengths
56
How do line spectra provide evidence for the existence of energy levels in atoms
Photons associated with particular energies show electron transitions up and down the discrete energy levels to provide the line spectra
57
Kinetic energy gained by accelerating electron through a potential difference =
eV
58
Why are only certain frequencies absorbed by atoms?
electrons can only exist in discrete energy levels
59
ground state
the lowest energy level where electrons are usually found
60
energy delivered by photon (hf) =
difference between the energy levels
61
how can electrons be excited?
- if a photon is absorbed | - if electrons are hit be other electrons
62
how is a photon emitted
electrons don't remain in an excited state so they de-excite and drop down to the ground state and emit energy in the form of a photon
63
high frequency photon means...
the more energy levels it jumps up
64
long wavelength photon means...
less energy levels moved up

A-Level PHYSICS Edexcel (16 decks)

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