Topic 5: Particle model of light Flashcards
What is a photon
A small packet of energy
What is wave particle duality
The idea that electrons can act as both a wave and a particle
Define wave phenomena
all the things that only waves can do
What are the 4 types of wave phenomena
Reflection,Refraction,Diffraction interference
What is planks constant
6.63x10-34
What two phenomena prove that Waves act as a particle
The photoelectric effect
Line spectra
What is planks constant theory
The idea that electromagnetic radiation is emitted is very small and the higher the frequency the higher the energy
What is the derivation for planks constant
E=∝f
E=kf
E=hf
What is work function
The minimum amount of energy required to release one electron from its ionic lattice in a metal
What is the threshold frequency
when the work function is equal to the photon energy
What is the equation for The energy of a photon
E=hf
What is the photoelectric equation
Hf=Φ +ke
What is the de broglie wavelength
λ=h/mv
define de broglie wavelength
Any particle with a momentum has an associated wavelength
Define the stopping potential
The work done against the electrons to cancel out the Kinetic energy
What is the exitation energy
The amount of energy required for an electron to escape from the surface of a metal
What is the ionisation energy
The amount of energy an electron needs to ionise and break free from its lattice
What is the photoelectric effect
Proof that light has a particle nature
Why is the wave theory for the photoelectric effect incorrect
Wave theory states that the longer the light is shone on the metal the more energy it has
Eventually low intensity light will still release enough electrons as it will build up energy
Explain the photoelectric effect
Electrons trapped in ionic lattice of metal due to positive charge
Electrons get energy from light waves in order to ionise and escape the metal
Once the electrons escape any residual energy is converted into kinetic energy as it it leaves the metal
Which need less energy to escape electrons closer to the top of the metal or the middle
Top
How many experimental findings are their for the photoelectric effect?
3
How do you convert from EV to J
/ 1.6x10-19
How do you convert from J to EV
x 1.6 x10-19
What is the gradient on a photoelectric graph
Planks constant
What is the y intercept on a photoelectric graph
Work function
what is the X axis on a photoelectric graph
Frequency
what is the Y axis on a photoelectric graph
Kinetic energy
What is the point at which the Kinetic energy is 0 on the graph
The fundamental frequency
What is the equation for stopping potential
work done =kinetic energy
VQ=1/2MV^2
What can the stopping distance be used for (3)
helps to find the kinetic energy of something small as e-
Can vary frequency & see how it affects KE
find the threshold frequency and work done
What is a photo vacuum cell
A component containing a photocathode and an anode that can produce photoelectrons.
Explain how a photo vacuum cell works
Explain how a photo vacuum cell works with a cell to generate a stopping potential
When a cell is added to produce a voltage in the opposite direction to the flow of the photoelectrons. When this voltage is high enough it can be used to stop the flow of photoelectrons. this us the stopping potential which we can use to measure the amount of photoelectrons we have in a a current.
