Engineering Physics: Unit IV: Basic Quantum Mechanics

Probability Density

Quantum Mechanics

Probability of finding the particle between positions x and x + dx

PROBABILITY DENSITY

Probability of finding the particle between positions x and x + dx


Probability density is maximum when


• For n = 1 (lowest energy state), x = a/2, i.e., the particle is most likely to be in the middle of the box (because is maximum there).

• For n = 2 (next energy state), the particle is most likely to be at and never found in the middle because is zero there.

• For n = 3, the most likely positions of particle are

The variation of probability densities (for n = 1, 2, 3) with x is shown in fig. 6.13.


It is noted that quantum mechanical results vary drastically from the classical results.

While classical mechanics predicts the same probability for the particle being anywhere in the box, quantum mechanics predicts that the probability is different at different points and there are points (nodes) where the particle is never found.


Engineering Physics: Unit IV: Basic Quantum Mechanics : Tag: : Quantum Mechanics - Probability Density