# How many photons per second is one Lumen? [closed]

Also the side question is how many Joules is one photon (any between 450-660nm). Thank you

P.S. I am asking because I want to estimate how much thermal energy should be dissipated by LED when part of known energy is emitted as light.

P.S. Got an answer from Robert. Thank you. So those 6500 Lumen 100Watt white LED arrays emit about 9 watt of energy in photons alone and rest 91W goes into heat. Not bad.

## closed as off-topic by rob♦Oct 26 '17 at 19:35

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Approximately $10^{15}$.

See this:

Photon flux of 540 nm light from the mechanical equivalent of light and the integrated spectral sensitivity of the human eye:

$3.8×10^{15}\ photons/s$ (photons per second)

$6.3×10^{-9}\ mol/s$ (moles of photons per second)

Also see this reference.

Note: this summarises Robert's answer in the question comments and is set to CW.