Under what conditions does quantum mechanics reduce to classical mechanics?

AI Thread Summary
Quantum mechanics reduces to classical mechanics when the energy difference between adjacent quantum states is comparable to thermal energy, specifically when the change in energy (ΔE) equals kT. The equation E=(n²h²)/(8mL²) is used to express energy levels, and the problem requires finding the value of mL² that satisfies this condition at a thermal energy of kT=4.28x(10^-21). By substituting n2=2 and n1=1 into the equation, one can solve for mL², noting that larger values of n2 will result in larger mL² values. The discussion highlights the challenge of dealing with multiple unknowns in the calculation. Understanding these relationships is crucial for determining the transition from quantum to classical mechanics.
amberbarton
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Homework Statement


"At 310K thermal energy kT=4.28x(10^-21). Use the equation you derived above (which I worked out to be E=(n²h²)/(8mL²) )to determine under which conditions quantum mechanics reduces to classical mechanics."
The hint was that "you need to find the value of mL² for which change in E between two adjacent energy levels is equal to kT".

Homework Equations


E=kt
E=(n²h²)/(8mL²)

The Attempt at a Solution


I'm not quite sure how to start here, the only thing I've managed to do so far is:

((n2²-n1²)h²)/(8mL²)=4.28x(10^-21)

I'm not sure what to do with so many unknowns, or what the question is actually asking me to calculate!
 
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amberbarton said:
...


I'm not quite sure how to start here, the only thing I've managed to do so far is:

((n2²-n1²)h²)/(8mL²)=4.28x(10^-21)

I'm not sure what to do with so many unknowns, or what the question is actually asking me to calculate!

Assuming the above is correct let n2 = 2 and let n1 = 1. Now solve for mL^2.

Larger values of n2 will yield larger values of mL^2 which you should point out.
 
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