Chemical Forums
Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: luketapis on March 26, 2012, 06:34:22 PM
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I have to do this excercis:
A desk lamp produces 5.0J of energy per second (5.0W) in the form of blue light of wavelength 470nm. How many photons of blue (470nm) light are emitted in 1 second?
Are there any equasion for number of photons emitted per second?
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well, using E = hv (v is actually "nu" = frequency), you can solve for frequency. Frequency is in Hz which is a cycle/sec (or sec^-1).
Hopefully this puts you on the right track
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"well, using E = hv (v is actually "nu" = frequency), you can solve for frequency. Frequency is in Hz which is a cycle/sec (or sec^-1).
Ok so:
V=E/h
V= 5/6.626 x 10^-34 = 7.5460 x 10^33 s^-1
But it doesn't help me at all :(
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In your equation you used E=5 Joules. Are you sure each photon emitted has an energy of 5 Joules? A photon at a certain wavelength will only have one energy, and, as a hint, it is not 5 joules. For a photon of light, a statement about its wavelength or frequency is a statement about its energy. Wavelength, frequency and energy of a photon are all interrelated via E=hf.
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"Wavelength, frequency and energy of a photon are all interrelated via E=hf"
what is f hear?
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"Wavelength, frequency and energy of a photon are all interrelated via E=hf"
what is f hear?
f is the frequency (the same as nu)...