The human eye responds to a light stimulus (generates a sensation of "light") upon receiving light energy of 10eV (and more). If we take 6000 angstroms as the average wavelength, how many photons must the eye receive to register a light sensation?

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asked by Peter
  1. How much energy do you have in 6000 A?
    E = hc/wavelength (w must be in meters) and E is then energy/photon.

    Then convert 10 eV to joules, and
    Joules = E/photon x # photons and solve for # photons.

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  2. PLS dR bob cna explain beter bcs i cant understand......thanks in advance

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    posted by Menes
  3. Hello Bob,

    I calculated it without converting to Joules by taking the planck constant with the eV as unit, but i get around 4.84 photons, which seems to be wrong. Any ideas?

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    posted by Peter
  4. Pete, the dimensional analysis is wrong. You should just convert the eV to joules.

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  5. even after converting to joules we get the same answer 4.835 which is wrong.

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    posted by KS
  6. Guys, the mathematics is correct. Look at what is being asked. It's simple.

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  7. Right... I was thinking the same along the lines of light is "quantized". Thanks!

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    posted by KS
  8. Determine the linear density of atoms (atoms/m) along the [111] direction of gold at 300K.

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    posted by Menes

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