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[NOTES/CM-06003] Particles --- Which area is the cross section?

For scattering of particles, we explain which area is scattering cross section.

[NOTES/CM-05006] Effective Potential for Spherically Symmetric Problems

Using angular momentum conservation it is shown that orbits for a spherically symmetric potential lie in a plane; This makes it possible to work in plane polar coordinates. The equation for radial motion becomes similar to that in one dimension with potential replaced by an effective potential. An expression for the effective potential is obtained.

[NOTES/QM-12002] Free Particle Wave Packets

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A particle with localized position is described by a wave packet in quantum mechanics. Taking a free Gaussian wave packet, its wave function at arbitrary time is computed. It is fund that the average value of position varies with time like position of a classical particle. The average vale of momentum remains constant and the uncertainty \(\Delta x\) increases with time.

[NOTES/QM-25005] Einstein $A$ and $B$ Coefficients

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