Is Total Energy Always Double the Kinetic Energy in Quantum Mechanics?

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Homework Help Overview

The discussion revolves around the relationship between total energy and kinetic energy in the context of quantum mechanics, specifically examining whether total energy is always double the kinetic energy for particles. The original poster presents equations related to energy and momentum, seeking clarity on their implications.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to derive a relationship between total energy and kinetic energy using equations for energy and momentum. Some participants question the applicability of certain equations to different types of particles, particularly photons versus ordinary particles.

Discussion Status

The discussion is exploring different interpretations of energy equations in quantum mechanics. Some participants have provided clarifications regarding the applicability of specific equations to photons and ordinary particles, but there is no explicit consensus on the original poster's assertion.

Contextual Notes

There is a distinction being made between the behavior of ordinary particles and photons, with some participants noting that certain equations may not apply universally. The original poster's assumptions about the relationship between total energy and kinetic energy are under scrutiny.

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Homework Statement



Ok so (1) E = hf and (2) lambda = h/p


Homework Equations





The Attempt at a Solution



For a particle mass m, speed v, momentum p

Surely if p^2 / 2m = Ek (kinetic energy)

then we can write from (2) Ek = h^2/ 2m lambda^2

But from (1) we can write E = hv/lambda => E = h(p/m)/lambda => E = h^2 / m lambda^2

This seems to imply that for such a particle total energy is always double KE. What's gone wrong?
 
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p^2 / 2m = Ek applies to ordinary particles, not photons.
Photons are WEIRD. The fact that p = h/λ applies to both is incredible and I think de Broglie thought of it while drinking beer.
 
Yes but I am talking about an ordinary particle here..
Does E=hf not work for ordinary particles?
 
E = hf applies to photons only.
 

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