De Broglie wave length, lambda=h/mv

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Discussion Overview

The discussion centers around the application of the de Broglie wavelength formula, specifically addressing the implications of calculating the wavelength for macroscopic objects, such as a stone, and its relation to the Planck length. Participants explore the concept of quantum mechanical effects and the limitations of observing such effects in larger bodies.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant asserts that the de Broglie wavelength for a 10 kg stone moving at 100 m/s results in a wavelength that exceeds the Planck length, questioning the feasibility of observing quantum mechanical effects in such a scenario.
  • Another participant calculates the de Broglie wavelength as 1.05 x 10^-37 meters and argues that this value is actually less than the Planck length, challenging the initial claim that it surpasses this limit.
  • A further response reiterates the calculation and questions how the wavelength could be considered to exceed the Planck length, emphasizing the need for a proper understanding of the implications of the formula.
  • One participant highlights that a stone is a macroscopic object composed of many fundamental particles, suggesting that blindly applying the formula without considering the context may lead to nonsensical conclusions.
  • A later reply supports the idea that the inability to observe quantum effects in larger objects may be due to their macroscopic nature, implying that quantum effects are typically confined to smaller scales.

Areas of Agreement / Disagreement

Participants express disagreement regarding the interpretation of the de Broglie wavelength in relation to the Planck length. There is no consensus on whether the wavelength exceeds the Planck length or the implications of this for observing quantum effects in macroscopic objects.

Contextual Notes

The discussion reveals limitations in understanding the application of the de Broglie formula to macroscopic objects and the assumptions involved in interpreting the results. There is an unresolved tension between the mathematical outcomes and the physical interpretations of quantum mechanics at larger scales.

matteo16
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for each massive body is assigned a wave length by the De Broglie formula: lambda=h/mv

but, for example, a stone which has a mass of 10 kg and which is moving with a speed of 100 m/s, is assigned a wave length that goes beyond the Planck length that is the limit.
how is this possible?
thus, if i want to see the QM effects on it i would to observe it at a distance lower than the Planck length
and this is impossible.
 
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Planck Length = 1.6 × 10^−35 meters

In your case, lambda = 1.05 x 10^-37 meters.

I don't see how this "goes beyond the Planck length". To see QM effects, the de Broglie wavelength has to be large enough to give observable effects.
 
scarecrow said:
Planck Length = 1.6 × 10^−35 meters

In your case, lambda = 1.05 x 10^-37 meters.

I don't see how this "goes beyond the Planck length". To see QM effects, the de Broglie wavelength has to be large enough to give observable effects.

1.05 x 10^-37 meters is lower than 1.6 x 10^-35(that is the limit) and so how this is possible?
how can this value surpass the limit?
 
for one thing, a stone is a macroscopic object, it is made up of a large number of "more fundemental" particles. you plug blindly into a formula (this could be called "proceeding formally") and you get an answer than doesn't make sense to you. this means you have to think about what you are doing and not just plug into a formula.
 
matteo16 said:
for each massive body is assigned a wave length by the De Broglie formula: lambda=h/mv

but, for example, a stone which has a mass of 10 kg and which is moving with a speed of 100 m/s, is assigned a wave length that goes beyond the Planck length that is the limit.
how is this possible?
thus, if i want to see the QM effects on it i would to observe it at a distance lower than the Planck length
and this is impossible.

That is right And that is one possible reason why nothing larger than a small molecule has ever demonstrated quantum effects.
 

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