Can Planck's Constant Equation Be Used to Calculate Particle Speed?

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Discussion Overview

The discussion revolves around the applicability of Planck's constant equation and related equations in calculating the speed of particles, specifically electrons. Participants explore whether the equations c=hv and c=lambda(v) can be used interchangeably with particle speed (u) in various contexts, including the relationships between frequency, wavelength, and speed.

Discussion Character

  • Exploratory
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • Some participants question whether the equation c=hv can be modified to u=hv for calculating the speed of a particle given its frequency.
  • Others point out that the equation c=hv is actually E=hv, indicating a potential misunderstanding of the equations involved.
  • One participant clarifies that the equation c=lambda(v) relates to the speed of light and asks if it can be used for particle speed instead.
  • Another participant asserts that the equation c=lambda(frequency) is specific to electromagnetic waves in a vacuum and suggests that other equations, such as the de Broglie relations, should be used for particles.

Areas of Agreement / Disagreement

Participants express differing views on the applicability of the equations for calculating particle speed, indicating that there is no consensus on whether these equations can be used interchangeably with particle speed.

Contextual Notes

There are unresolved assumptions regarding the conditions under which the equations apply, particularly the distinction between electromagnetic waves and particles, as well as the specific contexts in which each equation is valid.

fk378
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This is a general question..

For the equation c=hv
where c=speed of light, h=Planck's constant, and v=frequency...

Can u (speed of a particle/electron) be substituted in for c? ie, if given the frequency of an electron and we need to find its speed, can we use this equation (u=hv) or must we get to the answer by using other equations?
 
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fk378 said:
This is a general question..

For the equation c=hv
where c=speed of light, h=Planck's constant, and v=frequency...

Isn't this equation E=hv?
 
Oh sorry, I meant to refer to the equation c=lambda(v)
 
Soooo, what is the question?
 
For c=(lambda)(frequency)
where c=the speed of light, can you replace c with u (speed of a particle)? Say, you're given the frequency and the wavelength of a particle and you need to find its speed, can you use this equation, or must you find it from another equation(s)?
 
fk378 said:
For c=(lambda)(frequency)
where c=the speed of light, can you replace c with u (speed of a particle)? Say, you're given the frequency and the wavelength of a particle and you need to find its speed, can you use this equation, or must you find it from another equation(s)?
No, the equation you have quoted there is called the 'Dispersion relation for EM-waves in a vacuum' and is therefore only valid for EM-waves in a vacuum. You would have to use other equations, namely the de Broglie relations.
 
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