Homework Question 1B.9

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Homework Question 1B.9

Postby ariaterango_1A » Mon Oct 14, 2019 1:10 pm

Hi could someone help me with the set up of 1B.9? "A lamp rated at 32W (1W=1J.s^-1) emits violet light of wavelength 420nm. How many photons of violet light can the lamp generate in 2.0s? How many moles of photons are emitted in that time interval?

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Re: Homework Question 1B.9

Postby Ananta3G » Mon Oct 14, 2019 1:26 pm

Hello! So the way to approach this problem is as follows: You know that a 32 watt lamp can generate 32 J per second because 1 watt is equivalent to 1 joule/s. Thus, in 2 seconds, the lamp will emit 64 J of energy. Next, you need to find out how much energy is emitted per photon by using the wave length. To do so, you need to use E = hc/lambda. Once of you have done that, you should divide 64 J (the total amount of energy of the lamp) by the value you calculated for E to get the number of photons that was used for 64 J of energy. To get moles, just do dimensional analysis with Avogadro's Number. Hope this explanation helps!

Ziyan Wang 3J
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Re: Homework Question 1B.9

Postby Ziyan Wang 3J » Mon Oct 14, 2019 11:01 pm

Energy per photon=h*c/lambda=6.63*10^-34*3.00*10^8/(420*10^-9)=4.74*10^-19
Total energy= 32*2=64
# of photons= Total energy/energy per photon=64/(4.74*10^-19)=1.35*10^20

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