I wonder if Heisenberg principle (both [tex]\Delta p \Delta x \geq \frac{\hbar }{2}[/tex] and [tex]\Delta E \Delta t \geq \frac{\hbar }{2}[/tex]) can be applied to photons.(adsbygoogle = window.adsbygoogle || []).push({});

Say I have a laser emitting a flash. I know very well the wavelength of the photon, therefore its momentum. Also, I know well where it might be: it travels at c and must lie somewhere inside the cross section area of the laser beam situated at a distance ct from the laser, if I consider a time t after emission. Which seems to contradict that if I know well the momentum of the laser, I shouldn't know well where it is.

The same doubt arises with the relation between [tex]\Delta E[/tex] and [tex]\Delta t[/tex]. I know very well the energy of a laser photon since I know very well its wavelength. And I do so at any time...

Unless [tex]E\neq \frac{hc}{\lambda}[/tex]...

So I don't understand if I'm missing something or if Heisenberg's principle cannot be applied to photons.

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# Is Heisenberg principle applicable to a photon?

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