Page 1 of 1

### Quiz 1, Question 5

Posted: Mon Oct 31, 2016 8:13 pm
Could someone please explain how to do question 5 on quiz number 1? Fluorescence is the property in which molecules absorb and emit light where the photon emitted is lower energy than the photon absorbed. The energy unaccounted for is dissipated across the molecule. Diphenylanthracene (DPA) is a molecule of interest in solar technology because of the light it emits when excited. If a molecule of DPA is excited by 350 nm light and emits 425 nm light, how much energy did the molecule dissipate in joules? Thank you.

### Re: Quiz 1, Question 5

Posted: Mon Oct 31, 2016 9:27 pm
You use frequency= speed of light/wavelength for 350 nm and 425 nm and solve for frequency and then multiply each frequency by planck's constant (E=hv) (you get v= 7.058x10^14 for 425 nm and multiply by planck's to get 4.67x10^-19 J and you get v=8.57x10^14 for 350 nm and multiply by planck's to get 5.6794x10^-19 J) to get the Energy for each wavelength. Then subtract 350 nm's energy from 425 nm's energy and you get 1.01x10^-19 J (5.6794x10^19 J- 4.67x10^-19 J).