Section 2: Quantum Phenomena Flashcards
There are four conclusions made from the photoeletric effect what are they?
Conclusion 1 - for a given metal no photoelectons are emitted if the radiation has a freqency below a certain value
this is called the threshhold frequency
Conclusion 2-The maximum kinetic energy of photoelectrons increases with the frequency of radiation.
Conclusion 3 - The maximum kinetic energy of the photoelectrons is unaffected by varying the intensity of the radiation.
Conclusion 4- The number of photoelectons emitted per seconds is proportional to the intensity of the radiation.
Difine the intensity of radiation.
It is the amount of energy per second hitting an area of the metal
What type of electrons does the photoeletric effect refer to?
Delocalised elecrons in metal, so no refering the elecron levels!!
Describe how you can demonstrate the photo eletric effect.
A zinc plate is attached to the top of an electroscope cotaining a peice of metal with a srip of gold leaf attached.
The zinc plate is negatively charged. The negatively charged metal repels the gold leaf causing it to rise up.
UV light is then shone onto the zinc plate.
The energy of the light causes electrons to be lost from the zink plate via the photoelectric affect. The zink plate and metal lose their negative charge, gold leaf is no longer repelled and so falls back down.
How do elecrons move down energy levels?
By emitting a photon
What is the energy carried by an emmited photon from a elecrton that has de-excited?
The difference in energies between the two levels of the transition.
What is ioniasation energy?
The amount of energy needed to remove an electron from the ground state atom.
What does line emission spectra Provied evidence for?
That electrons in atoms exist in discrete energy levels.
- Atoms can only emit photons with energies equal to the difference between two enegy levels.
- So you can only see corisponding wavelengths in the line spectra
A diffraction patter is formed by passing monocromatic light through a single slit.
The width of a single slit is reduced, what happens to the width of the central maximum and the intensity of the central maximum?
Width of cantral maximum increases
The intensity of central maximum decreases
What is the area of a current time graph = to?
Charge
Describe the behaviour of electrons which demnonstrates that they have wave properties.
Electrons may diffract by crystal lattice
to produce a ring
ect need to finish
What is the particle model?
4 points
One photon interacts with one electron
Each photon has energy proportional to frequency
The electron is emitted only if the energy of the photon is greater than the work function
Any photon energy over and above the work function is gained by the electronn as kinetic energy.
What is the wave model?
Would be exected that the energy of the electron would build up and eventually be emmited
The kinetic energy of the emmited electrons would depend on the intensity of the wave and not the frequency.
Electron diffraction
Increasing the wave length will do what?
More lines in the diffraction pattern
Electron diffraction
What will slowing the speed of the electrons do?
The rings will be more widely spaced
(might increase the wavelength ,im pretty sure)
