## HW Problem 1.27

$E=hv$

kellyz_1C
Posts: 33
Joined: Fri Apr 06, 2018 11:05 am

### HW Problem 1.27

I'm conufsed on how to start this question. Can anyone help me?

Celeste Martinez 1K
Posts: 31
Joined: Fri Apr 06, 2018 11:04 am
Been upvoted: 1 time

### Re: HW Problem 1.27

Since 1 W= 1 J/s and there are 32 W then you basically have 32 J/s. The problem is asking us for how many photons can be generated in 2 seconds. Therefore, we get 32*2= 64 J. In this case we will use the equation E=h*c/Lambda since we already have the wavelength (420 x 10^-9 m).
Multiply Planck's constant (h) = (6.63 x 10^-34 Js) and the speed of light (c) = 3.0 x 10^8 m/s and divide by wavelength (420 x 10^-9 m). The answer comes out to be 4.7 x 10^-19 J/photon.
You will then get the number of photons by dividing 64 J by the previous answer (4.7 x 10^-19). The answer should be 1.4 x 10^20 photons.
Since they also ask us for how many moles of photons are emitted, you must divide your previous answer (1.4 x 10^20) by avogadro's number (6.022 x10^23)

Hope this helped!

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