Practice Textbook Problems



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Ethan Goode 3H
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Joined: Wed Sep 30, 2020 9:51 pm

Practice Textbook Problems

Postby Ethan Goode 3H » Sun Oct 25, 2020 11:46 pm

A lamp rated at 32W(1 W=1 J⋅s−1) emits violet light of wavelength 420 nm. How many photons of violet light can the lamp generate in 2.0 s? How many moles of photons are emitted in that time interval?

Which equation would you use to do this problem? I am struggling starting.

Chem_Mod
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Re: Practice Textbook Problems

Postby Chem_Mod » Mon Oct 26, 2020 12:07 am

Hi, you would use the E = hv equation. Don't forget that the E in that equation is Energy per photon (in other words J/photon). Sometimes if you're stuck, you can try looking for ways to cancel units to get your final result, which in this case is photons. I hope this helps you start this question.

anikamenon1L
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Re: Practice Textbook Problems

Postby anikamenon1L » Mon Oct 26, 2020 10:11 am

For this problem, the first thing you need to do is find the energy per photon, using E = hc/λ. Once you find the energy per photon, you should calculate the total energy the light is providing in the 2.0s (which would be 64 W or 64 J/s). Then you can divide the total energy (64W) by the energy per photon that you calculated to find out how many photons are being emitted by the lamp. Then use Avogadro's number to find how many moles of photons are emitted in that same interval.

Hope this helps!


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