Why is the velocity of an H2 molecule after colliding with a 60nm photon so low?

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SUMMARY

The final velocity of an H2 molecule after colliding with a 60nm photon is approximately 3.5 m/s, which is significantly low despite the high energy associated with the short wavelength. This low velocity is attributed to the relatively large mass of the H2 molecule, which results in a smaller change in velocity upon absorbing the photon's energy. The discussion emphasizes the importance of understanding momentum conservation in such collisions and challenges common misconceptions regarding energy and mass in molecular dynamics.

PREREQUISITES
  • Understanding of momentum conservation principles
  • Basic knowledge of photon energy and wavelength relationships
  • Familiarity with molecular mass and its effects on velocity
  • Concepts of internal excitation energy in molecules
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  • Study the relationship between photon energy and wavelength using the equation E = hc/λ
  • Explore the principles of momentum conservation in elastic and inelastic collisions
  • Investigate the effects of molecular mass on kinetic energy and velocity
  • Learn about internal energy states and excitation in diatomic molecules like H2
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This discussion is beneficial for physics students, molecular physicists, and anyone interested in the dynamics of molecular collisions and energy transfer processes.

physgirl
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So if a H2 molecule collides with and absorbs a photon of wavelength around 60nm, I find the final velocity of H2 molecule (assuming momentum's conserved in collision) to be around 3.5 m/s, which I think is very small... I would have thought that since the wavelength of the photon is so small, the energy of it is pretty high, which means H2 should move much faster than just 3.5 m/s after the collision... it just doesn't make sense to me conceptually, I guess. Is there something wrong with my logic?
 
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Only in questioning your answer, which is correct.
The velocity is slow because H2 is so massive.
Preconception is the mother of confusion.
 
Hi. Just curious. What text did this question come out of? Are there any further questions about the internal excitation energy of the H2 molecule after the collision?
 

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