em spectrum, de broglie, pe notes
Post on 10-Jul-2015
Embed Size (px)
de Broglie Wavelength
de Broglie Pictured the electron in its circular orbit as a
particle wave Can produce "standing waves" under
resonant conditions Developed the idea that a particle with mass,
m, and a velocity, v, has a wavelength associated with it => de Broglie Wavelength
Schrdinger Used de Broglie wavelength to
create a quantum theory based on waves
Did not keep the "orbits" The wave/particle model cannot
determine the location and momentum of an electron at the same time
The quantum model predicts the probability that an e- is at a specific location
Heisenberg Uncertainty Principle Can only determine the
location or the momentum (velocity) of the particle - not both at the same time!
Photons and Photoelectric Effect
Metal is illuminated by electromagnetic radiation
Energy that is absorbed near the surface can free electrons, causing e's to fly off
Released electrons are called photoelectrons
Significant time delay between the illumination and ejection - build up of KE to free e-'s
Increasing the intensity of light = cause electrons to leave with greater KE
Photoelectrons would be released regardless of frequency of light, as long as the intensity was great enough....
But these are FALSE!
Wave theory predicts the following:
Photons were ejected immediately Increasing the intensity did not change the KE
although more e-'s were ejected, KE does not increase. If the frequency fell below a threshold (specific for
each metal), no photoelectrons would be ejected, regardless of intensity!
If the frequency increases above the threshold, KE increases linearly
PE Effect - Math
Threshold Frequency Work Function - the minimum
amount of energy required on a metal surface to eject an electron
How are these two related?
PE Effect - Math