Relevant Mr. Lovenstein comic: https://lemmy.world/post/8457726

As a man who used to have long hair for decades, this is just wrong. But also, usually using more than one shampoo + one conditioner is not going to make much difference.

Baby Shark. Because… it kinda looks like a shark? (Blue Mitsubishi Outlander Sport/ASX, depends on the country)

A laser, maybe, but definitely not LEDs. Vapor/gas lamps produce the narrowest frequency bands possible, because it comes from very well defined atomic transitions (Hz range). LEDs produce frequency bands with widths in the GHz/THz range, while semiconductor lasers can maybe reach KHz if they are really good. So, unfortunately, for this type of applications, vapor lamps would probably still be needed.

Source: I work with lasers and spectroscopy.

Edit: very good idea about using non-visible light!

It takes some fiddling, but it works, and is fantastic!