Confused to the max Re-aranging equations.

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SUMMARY

The discussion centers on the manipulation of equations in physics, specifically the equations E=hc/λ and λ=h/mv. The user incorrectly substitutes these equations, leading to the conclusion that velocity equals twice the speed of light, which is fundamentally flawed. A participant clarifies that E=hc/λ represents energy per photon, while λ=h/mv denotes the de Broglie wavelength for a non-relativistic particle, emphasizing that substituting these equations without understanding their contexts results in nonsensical outcomes.

PREREQUISITES
  • Understanding of the equation E=hc/λ and its application in photon energy.
  • Familiarity with the de Broglie wavelength equation λ=h/mv.
  • Basic principles of conservation of energy in physics.
  • Knowledge of non-relativistic particle dynamics.
NEXT STEPS
  • Study the implications of the de Broglie wavelength in quantum mechanics.
  • Explore the concept of photon energy and its relationship with wavelength.
  • Investigate the principles of relativistic physics and limitations of classical mechanics.
  • Learn about the conservation of energy in various physical systems.
USEFUL FOR

Students preparing for AS level physics exams, educators teaching physics concepts, and anyone interested in the foundational principles of energy and wave-particle duality in quantum mechanics.

slawted
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Okay so today i sat a AS level physics paper and after finishing the exam i looked threw the equation booklet and decided to do some manipulation and i came up with this and was wondering what you guys think of it. I am confused! :)

E=hc/λ AND λ=h/mv
subbing in gives E=hcmv/h which is E=cmv
conservation of energy...
cmv=1/2mv^2
2c=v

how can velocity = 2*speed of light?

Thoughts?
 
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slawted said:
Okay so today i sat a AS level physics paper and after finishing the exam i looked threw the equation booklet and decided to do some manipulation and i came up with this and was wondering what you guys think of it. I am confused! :)

E=hc/λ AND λ=h/mv
subbing in gives E=hcmv/h which is E=cmv
conservation of energy...
cmv=1/2mv^2
2c=v

how can velocity = 2*speed of light?

Thoughts?

Just because something has the same name or the same symbol, does not mean they are representing the SAME thing.

E=hc/\lambda is the energy per photon with that particular wavelength, whereas \lambda=h/mv is the deBroglie wavelength for a non-relativistic particle with mass m at velocity v!

You can't simply substitute apples into oranges. If you do that, you get ridiculous answer like what you got.

Zz.
 

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