How can the uncertainty relation be written as such

AI Thread Summary
The discussion revolves around deriving the uncertainty relation Δλ Δx ≥ λ^2 / 4π. The initial attempt incorrectly substituted terms and led to confusion about the constants involved. Participants clarified that the correct approach involves recognizing the relationship between momentum and wavelength, specifically p = h/λ, and applying the uncertainty principle accurately. The mistake in handling the differentiation of terms was also addressed, emphasizing the distinction between Δ(1/λ) and 1/Δλ. Ultimately, the clarification helped resolve the confusion regarding the factor of 4π in the final expression.
Abdul.119
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Homework Statement


Show that the uncertainty relation can be written as
Δλ Δx >= λ^2 /4π

Homework Equations

The Attempt at a Solution


Ok the uncertainty relation is ΔpΔx >= h/2π , also p = h/λ , so substituting that I have Δh/λ Δx >= h/2π , then divide both sides by h, and multiply both sides by λ^2, so I get Δλ Δx >= λ^2 /2π , which is still not the same as the one given, I don't understand how the 2π becomes 4π
 
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The minimum uncertainty is ##\displaystyle \frac{\hbar}{2}##.
 
Abdul.119 said:
Ok the uncertainty relation is ΔpΔx >= h/2π
Are you sure about that?

Abdul.119 said:
also p = h/λ , so substituting that I have Δh/λ Δx >= h/2π
I don't understand what you are doing here. How can you have Δh?
 
Abdul.119 said:
Δh/λ Δx >= h/2π
I assume you mean Δ(h/λ) Δx, which is hΔ(1/λ) Δx
Abdul.119 said:
multiply both sides by λ^2
But that isn't what you did.
Δ(1/λ) is not the same as 1/Δλ. What does it turn into?
 
Right I had a mistake in the uncertainty relation that's why I was confused. I took care of it now, thank you for the help.
 
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