Timeline for What actually is white light?
Current License: CC BY-SA 4.0
8 events
| when toggle format | what | by | license | comment | |
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| Jan 18, 2022 at 8:01 | comment | added | Ruslan | @MarkRansom yeah, I know it pretty well, thanks :) | |
| Jan 18, 2022 at 4:47 | comment | added | Mark Ransom | @Ruslan you might be interested to know that's how most white LEDs work. A blue LED is coated with a phosphor that absorbs some of the blue and emits yellow. Now the yellow isn't a single frequency, but it's balanced to be complimentary to the blue. And different formulations will give different white points, which is why there are both warm and cool white LEDs. | |
| Feb 15, 2021 at 17:42 | comment | added | Ruslan | Just look at the chromaticity diagram. Choose a white point (e.g. D65, as for sRGB) and draw a straight line through it, trying not to intersect the line of purples (you'll still have some room to choose the slope). You'll get two intersections of this line with the gamut boundary, which are the two wavelengths you need to achieve your chosen white point. Then it's just the matter of weighing the powers of light sources to move the mixture along the line to achieve the white point. | |
| Feb 15, 2021 at 17:29 | comment | added | jamesqf | @Ruslan: Interesting. I would have thought it would take at least three, one for each type of cone cell. Though if the light's dim enough to activate only rods, it's always perceived as white. Which just goes to show that physics and perception are quite different. | |
| Feb 14, 2021 at 14:19 | comment | added | Ruslan | In fact, it's sufficient to have two spectral lines (and nothing else) in the spectrum to see the light as white. E.g. $571\,\mathrm{nm}$ and $460\,\mathrm{nm}$ (or near these) in appropriate proportions. | |
| Jan 8, 2021 at 19:07 | comment | added | jamesqf | @user253751: But that is just linguistic shorthand for "evenly distributed over all (visible?) frequencies". Indeed, if we consider sunlight as white light, it's not evenly distributed in the visible light range, being rather more intense in the blue than the red: fondriest.com/environmental-measurements/parameters/weather/… | |
| Jan 8, 2021 at 17:05 | comment | added | Criticizing Israel not allowed | I daresay that the physics meaning of "white light" necessitates all frequencies. | |
| Jan 8, 2021 at 3:03 | history | answered | jamesqf | CC BY-SA 4.0 |