Electromagnetic radiation and Quantum effects Flashcards
Photoelectric effect
When photons of EM waves are incident on a material and release electrons from the material
Threshold frequency
The minimum frequency of EM radiation that will release photoelectrons (with zero K.E)
Work Function
The minimum energy that an electron needs to break the bonds holding it and escape the surface (with zero K.E)
K.E of photoelectrons are independent of intensity because……..
The electrons can only absorb on photon at a time. Higher intensity means more photons per second not higher energy photons
Electron-Volt (eV)
The amount of kinetic energy gained by an electron when it is accelerated through a pd of 1 volt
Ground State
The lowest energy level in an atom
Excitation
The movement of electrons to higher energy levels
Ionisation
When an electron is completely removed from it’s atom the atom is said to be ionised
Ionisation energy
The energy required to remove an electron from an atom, from the
Electrons move up energy levels when….
they absorb a photon
Electrons move down energy levels when
They emit photons
Briefly state processes involved in fluorescent tubes
electrons emitted by electrodes are accelerated
high speed electrons collide with mercury atoms
orbital electrons absorb photon and are excited
Orbital electrons move down energy levels emit UV photon
UV photon collides with phosphor coating
Phosphor electron excited
Electron relaxes and cascades down energy levels emitting many lower energy photons
Continuous spectrum
White light produces this, all the colours and no gaps
Line spectrum
not continuous but lines that correspond to particular wavelengths. these correspond to particular energy level transitions
Line absorption spectra happens when
Light with a continuous spectrum passes through cool gas. Photons are selectively absorbed corresponding to allowed energy level transitions. Gaps appear in the spectrum
