At what velocity should relativity be taken into account

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Homework Help Overview

The discussion revolves around the conditions under which relativistic effects should be considered in physics problems, particularly in the context of the photoelectric effect and related concepts. The original poster is evaluating a specific velocity of an electron and questioning whether this velocity necessitates the application of relativity.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • The original poster seeks clarification on the threshold for considering relativity based on a calculated velocity. Some participants discuss the relationship between the given velocity and the speed of light, questioning the significance of the percentage of light speed represented by the electron's velocity.

Discussion Status

The conversation is ongoing, with participants exploring the implications of precision in calculations and the relevance of relativistic effects at certain speeds. There is acknowledgment of the original poster's concerns, and some guidance has been offered regarding the relationship between velocity and the speed of light.

Contextual Notes

The original poster mentions upcoming exams, indicating a context of preparation and the need for clarity on when to apply relativistic principles. There is a reference to potential future questions involving higher velocities, suggesting a broader concern about understanding these concepts.

moonkey
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Homework Statement


I have exams coming up and I'm just looking for an idea of when relativity should be taken into account. For example I'm just going over a question involving photoelectric effect and potential fields and de Broglie and all that jazz and the final velocity of the electron turns out to be around 6.5x106ms-1. Should I take relativity into account for this velocity or is it still safely within the margins of non-relativistic velocity? I'm thinking that it is safe to assume that it is non-relativistic but I would like some advice just in case such a question arises that involves a greater velocity.


Homework Equations





The Attempt at a Solution

I have exams coming up and I'm just looking for an idea of
 
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OOPS. Forget I said anything (it turned out to be not relevant, so I deleted my comment)
 
At a first glance, I'd say it depends on the precision that you want.
Since c is 300.000.000 m/s your speed is a 2% of c, which gives you an error of 0.03% if you ignore c (if I am not wrong).

If you use just only 3 figures (e.g. 0.134) in your data, then ignore it.
 
That makes perfectly good sense.

Thanks Quinzio
 

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