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Optoelectronics, Optics, Lights and Lasers
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How many photons are emitted?
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Topic: How many photons are emitted? (Read 370 times)
A
Newbie
Posts: 21
How many photons are emitted?
«
on:
May 28, 2011, 06:30:39 AM »
How many photon/s are emitted by a green light (λ= 500 nm) 60 W incandescent bulb? Assume an efficiency of 2%.
Don't understand the efficiency part...if anyone could help i'd appreciate it!
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Zaghawa
Newbie
Posts: 5
Re: How many photons are emitted?
«
Reply #1 on:
May 28, 2011, 09:35:52 AM »
Calclate the theoretical number. The efficiency part means that only 2% of that number will be emitted.
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Alone_GuY
Newbie
Posts: 12
Re: How many photons are emitted?
«
Reply #2 on:
May 28, 2011, 10:30:43 AM »
Power = N x Energy
Energy = hc/λ
Energy = 6.62 x 10^-34 x 3 x 10^8/ 500 x 10^-9
Energy = 4 x 10^-19J
Power = 60W
N = 60 x 10^19 /4
N = 15 x 10^19
Efficiency is 2% that means only 2% of the calculated N will be emitted.
So final answer is 3 x 10^18
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