## Question 1.25 (Sixth Edition)

$c=\lambda v$

Steve Magana 2I
Posts: 61
Joined: Fri Sep 28, 2018 12:24 am

### Question 1.25 (Sixth Edition)

Question: Sodium vapor lamps, used for public lighting, emit yellow light of wavelength 589 nm. How much energy is emitted by (a) an excited sodium atom when it generates a photon; (b) 5.00 mg of sodium atoms emitting light at this wavelength; (c) 1.00 mol of sodium atoms emitting light at this wavelength?

I'm having difficulty with how to approach this problem. Thank you!

Posts: 60
Joined: Tue Nov 28, 2017 3:02 am

### Re: Question 1.25 (Sixth Edition)

For part a) you should solve for frequency (v) from the wavelength given. Therefore use the equation which relates wavelength and frequency: c = λν. Using that wavelength use the Energy of the photon equation to solve for energy: E = hv.

For part b) use number of photons per mole constant in substitute for Planck's constant. This will convert it to a useable value in meters (just like h) then multiply it to the energy calculated in part a).

For part c) use the same equation but instead convert 1 mole Na into grams.

Example 1.4 in the book (6th ed.) shows how to do this whole problem.