Hacker News Reader

Is it the UV, or just the visible lights? i.e., can you get some of the benefit from LEDs at sunlight temperature?

UV-B makes your body produce Vitamin-D.

So, special LED that can emit UV helps for that, too, but carefully.

Oh and ordinary window glass completely blocks UV rays.

Glass actually fully blocks the helpful UV-B rays while still allowing some amount of harmful UV-A rays through.

There is an interesting illustrating picture about this. From a trucker where the sun always only hit one side through glass: