## frequency question

For electromagnetic radiation with a wavelength of 576.3nm, what is the frequency of the radiation in s^-1? What is the energy in J of one photon of the radiation? What is the energy in kJ of one mole of photons of the radiation?

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I think I have the answer.

For the frequency, I did nu=c/lamba

nu = 2.9979x10^8/(576.3)
nu = 520197.8136
= 5.202 x 10^5

For the energy in J, I did:
6.6256x10^-34 x 5.202x10^5 = 3.447 x 10^-28

For the last part, I figured out the mols but don't know where to go from there:

3.447x10^-28 x 6.022x10^23 = 0.0002076mols

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 Yeap, everything seems okay for me. Just have to be careful with the SI unit, for example, convert pm to To calculate the energy in kJ of one mole of photons of the radiation, multiply the answer obtained in part (b) with Avogadro constant. Then you will get the answer in unit Joule. remember to divide it by 1000 to change the unit to the required KJ.
 lkh - i am not sure what you mean - is that for a)?

## frequency question

lkh1986 mentioned several things.

1. Careful with units. If c is given in m/s, then wavelength must be in m, in order to give frequency in s-1. 1 nm (nanometer) = 10-9m

2. E = h$\nu$, where E is energy, h is Planck's constant and $\nu$ is frequency. Again make sure units are consistent.

 What is the energy in kJ of one mole of photons of the radiation?
Here one is presumably being asked for the energy of 6.0223 x 1023 (Avogadro's number) photons of the energy calculated previously for a single photon. 1 kJ = 1000 J.
 astronuc, thanks. so for the first one, instead of using 576.3nm, I would then multiply that by 10^-9m/1nm, so I get 5.76 x 10-7?