Photon flux converter
Convert optical power into photons a second. Pick the wavelength first: a blue photon carries more energy than a red one.
That's 1,278,665,606× as bright as a sensitive detector, while a laser pointer is 2.3× more. That is about 0.002123 µmol of photons a second.
What it means
How many photons?
This counts photons arriving, not photons detected. A detector’s quantum efficiency decides how many of them are actually recorded.
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Learn
Three things worth knowing
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A milliwatt of green is 2.7 × 10¹⁵ photons
Every second. At 1550 nm the same power is nearly three times as many photons, because each one carries less energy.
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Einstein, and the photoelectric effect
His 1905 paper — the one that won the Nobel Prize, not relativity — showed that light arrives in packets whose energy depends only on frequency.
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Power is not photon count
Two lasers of equal power at different colors emit different numbers of photons. For anything that counts photons — photosynthesis, detectors, photochemistry — the count is what matters.
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Background
About photon flux
Light can be measured as power or as a count of photons, and converting needs the wavelength: E = hc/λ. A green photon at 532 nm carries 3.7 × 10⁻¹⁹ joules, so a one-milliwatt laser pointer emits about 2.7 × 10¹⁵ of them every second.