QUANTUMN PHENOMINA Flashcards
Assuming radio waves on left and gamma rays on right, what happens to frequency and wavelength as you go along?
The wavelength would get shorter and the frequency would increase.
State the equation relating speed of light to a wave.
C = f lamba
State the equation for photon energy.
E = hf or E = hc/ lambda
Define work function.
The minimum energy required to release an electron from the surface of a metal.
Define Ekmax.
The minimum kinetic energy of an emitted electron.
Define an Electron Volt.
The energy gained by an electron that is accelerated over a potential difference of 1V.
Recall the POWER acronym.
Photon energy is E =hf.
One photon interacts with one electron.
Work function is the minimum energy required to release an electron from the surface of a metal.
Electron energy must be equal to or greater than the work function of the metal for electrons to be released.
Remaining energy is the maximum kinetic energy of the electron.
Define Stopping Potential and give the equation.
The potential difference needed to stop the fastest electrons from leaving.
Vs = Ekmax/ charge of electron.
Describe how gas discharge tubes work.
Electrons are accelerate through a low pressure gas and collide with gas atoms.
If the electrons have enough kinetic energy they can transfer some of the energy to the atom.
Atoms can become ‘excited’ by gaining energy if the electron can make it up to the higher energy electron shell.
Atoms in ‘excited’ state Is unstable and loses energy. The atom ‘de-excites’ falling down through energy levels emitting photons with each jump.
Define Ionisation.
An atom that has gained or lost electrons and so is charged.
Describe how fluorescent tubes work.
Glass tube contains Mercury vapour at a low pressure giving electrons sufficient time to gain ke.
Electrons released from cathode accelerate towards the anode.
Some collide with Mercury atoms:
Some ionise producing more accelerating electrons while some excite then de-excite.
This emits photons of UV light and some visible.
Photons of UV light absorbed by atoms in coating of tube. They excute then de-excite emitting light of lower energy hence longer wavelength.
