Locked in set - Quantum Physics Flashcards
(17 cards)
What is a photon?
A discrete packet of energy called a quantum
What is the equation for accelerating p.d?
eV= 1/2mv^2
What is an electronvolt?
The kinetic energy gained by an electron accelerated through a potential difference of 1V
How would you carry out an experiment to estimate the plank constant?
Circuit:
Variable resistor, LED of know wavelength, voltmeter over LED, power supply, milliameter for better precision
Experiment:
Start with no current
Adjust reisistor until current flows / LED lights up
Note voltage at this point
Plot voltage against 1/wavelength
Gradient = hc/e
What is the photoelectric effect?
Free electrons on surface absorb energy from light
If an electron absorbs a photon with enough energy to break the bonds holding it it will be emitted as a photoelectron
What conclusions can be drawn from the gold leaf experiment?
Intensity is proportional to the rate of emission
No photoelectrons are emitted if the frequency of light is below a certain value
Maximum kinetic energy is dependent on frequency not intensity.
What is wave theory?
Energy is spread evenly across the wavefront
Energy carried is proportional to intensity for a certain frequency
Each free electron would gain some energy from each incoming wave
Eventually each electron would gain enough energy to leave
What is the photon model?
Metal is bonbarded by photons
When a photon is absorbed the electron will gain energy equal to hf
How does the photon model explain threshold frequency?
If energy gained is greater than work function then the electron is emitted
If the energy is not the matal will heat up but no electrons will be emitted
hf > work function from emission
How does the photon model explain max kinetic energy?
Minimum it can loose is the work function so hf - work function = kinetic max
What is evidence for light as a wave?
What is evidence for light acting as a particle?
What is the wave particle duality theory?
How did electron diffraction prove wave nature?
Which equation is Einsteins photoelectric equation?
How did they carry out electron diffraction?
How is photon rate of emission related to intensity?
