3.2.2 Quantum Flashcards
What is the Photoelectric effect?
1.Where photoelectrons are emitted 2.from the surface of a metal
3.due to light of a certain frequency is incident on it
What is the threshold frequency?
The minimum frequency of EM radiation required to remove/liberate electrons from the surface of a metal
What is the Work function?
The minimum energy required for electrons to be emitted from the surface of a metal
What is stopping potential?
The potential difference required to stop photoelectron emission from occurring
What is the photoelectric equation?
E = h f = ϕ + Ek (max)
What is maximum kinetic energy?
The maximum kinetic energy of the
photoelectrons.
What is meant by excitation?
Electrons moving up energy levels
Electrons can only exist at …..
Discrete energy levels
What are three ways that electrons can gain energy/ move up energy levels? (3)
Absorbing photons
Colliding with free electrons
Physical factors such as heat
What is ionisation?
When an electron gains enough energy to be removed from the atom
If the energy of the free electron is greater than the ionisation energy then…..
Ionisation occurs
1eV = The ….. gained by one ….. when passing through a ….. difference of 1 volt
Energy, electron, potential
1eV = how many joules
1.6 x 10^-19 J
What is a fluorescent tube filled with?
Mercury gas, Phosphorus lining
How are free electrons in a fluorescent tube accelerated?
A high potential difference is put across the tube
How are UV photons emitted by the mercury atoms within a fluorescent tube?
The accelerated free electrons collide with and excite mercury atoms which then move down energy levels via emitting a UV photon
How do the Phosphorus atoms emit visible light photons?
The phosphorus electrons absorb UV photons, exciting them, then they fall in energy levels via emitting a visible light photon
What are three ways that electrons can move up energy levels? (3)
Collisions with other atoms or electrons
Absorbing a photon
Physical sources, such as heat
Excited atoms emit light of certain ….. , which correspond to different …..
Wavelengths, colours
Each element produces ….
A unique set of spectral lines
No two elements emit the same set of …..
Spectral lines
Elements can be identified by their …..
line spectrum
What two types of line spectra are there?
Absorption and emission
Spectral lines are evidence for …..
Transitions between discrete energy levels
What is the name of the lowest energy level avaliable?
The ground state
When electrons transition from a higher to a lower energy level…..
A photon is emitted
For emission spectra, what does each transition correspond to?
To a different wavelength
For emission spectra, what is each photons wavelength associated with?
A discrete energy level
For absorption spectra, what is found when white light is passed through a low pressure and cool gas?
Certain wavelengths are missing
What does the absorption spectra consist of? (Ignore the missing wavelengths)
A continuous spectrum
What are the wavelengths that are missing from absorption spectra the same as?
The corresponding emission spectra of the same element
What is a difference in energy levels equal to?
A specific photon energy
What is a piece of evidence which shows that light can behave as a wave?
Diffraction
What is special about diffraction?
It is a characteristic that only waves have
What is a piece of evidence which shows that light can behave as a particle?
The photoelectric effect
What is the name of light behaving as a packet?
A photon
What sort of interaction do photons have?
A one to one interaction
What does wave theory suggest about the frequency of a wave?
That any frequency of light could remove/liberate electrons, if given enough time and exposure
What does wave theory suggest about energy absorbed by each photon?
That the energy absorbed by each electron will increase gradually with each wave
What does the particle theory of light show about electrons emitted when exposed to light?
Electrons are either emitted or not emitted when exposed to light
What does the particle theory of light show about energy absorbed by each electron?
Energy is absorbed instantaneously
What does the particle theory of light show when intensity of light is increased?
More photonelectrons are released per second
What does the particle theory of light show when intensity of light is decreased?
Less photonelectrons are released per second
What properties have electrons shown that they have?
Particle and wave-like properties
How can electrons wave-like properties be observed?
Electron diffraction
Regarding electron diffraction, the amount of diffraction changes due to what?
The particle’s momentum change, which is due to the change in wavelength
Regarding electron diffraction, what is wavelength inversely proportional to?
Momentum
Regarding electron diffraction, if wavelength increases, momentum….
Decreases
Regarding electron diffraction, if wavelength decreases, momentum….
Increases
What must happen to scientific theories before they become validated?
They must be evaluated and peer reviewed
….. and …… of the nature of matter has changed over time
Knowledge and understanding
