Recap of last lecture
Looked at 4 phenomena which are problematic for classical physics
Line spectra and black body radiation spectrum can be explained in
terms of discrete energy levels in atoms where E
1
–
E
2
= hf;
The same particle like properties of light can also explain the
photo-electric effect and Compton scattering.
E
photon
= hf

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De Broglie waves
Just as light can behave both as particles and waves
Similarly matter particles can behave as waves
Wavelength of matter particle =
l
= h/p =h/mv
Wave nature of electrons implies that they can only have
certain quantized (discrete) angular momenta as they
orbit the atom (because the circumference of the orbit
must be an integer multiple of the wavelength)
L = mvr = hr/
l
= h (2
p
r
/l)/2p
= nh/2
p
Therefore the linear momentum/energy
of these electrons are also discrete

Two-slit interference
•
The predicted maximum “grows in” as the quantity of measurements
increases.
Animation of 2 slit experiment with electrons

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