Comment by SyzygyRhythm
3 hours ago
> that's why they were the color they were
That doesn't seem right to me. Sodium (and mercury) vapor lamps are the color they are due to physics, and were chosen because they're very efficient (and long lasting). Low-pressure sodium is the best and worst of these; essentially monochromatic but fantastic efficiency. Their only advantage, color-wise, is that the light can be filtered out easily (they used to be widely used in San Jose because Lick Observatory could filter out the 589 nm light).
...And the old Engineer was just saying that that was the area on the spectrum they aimed for, so they found a light that emitted in that wavelength that could be technically implemented and scaled.
Way better work than whoever it is handling this LED nonsense. Why we can't find a diode that we can use to simulate the old spectra would be a fun research project.
We of course can make LEDs of more or less any color. The current white LEDs are high-power blue LEDs that are covered by various phosphors to give a mix of colors for "full spectrum" illumination. Different color temperatures are produced by different mixes of phosphors. This is pretty similar to how the traditional luminescent (mercury vapor-based) lamps worked.
But different phosphors have different efficiency and price. LED lamps were first introduced for interior lighting, where sun-like spectrum is welcome. Such LEDs were produced en masse and relatively cheaply. So street lighting naturally used them, because municipalities usually look for the cheapest viable option.
We likely could produce high-power narrow-spectrum orange LEDs if there was a large market for the economies of scale to kick in. You can buy deep orange LED lamps today (look for color temperature 1800K or 1600K, "amber"), but they are more expensive, because they are niche.