# De Broglie wave length, lambda=h/mv

## Main Question or Discussion Point

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

but, for example, a stone wich has a mass of 10 kg and wich 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.

## Answers and Replies

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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.

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?

olgranpappy
Homework Helper
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 doesnt make sense to you. this means you have to think about what you are doing and not just plug into a formula.

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

but, for example, a stone wich has a mass of 10 kg and wich 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.