Eli5 why fluorescent and neon colors glow brighter under black light then other colors

Question

I was looking in the blacklight I have in the bathroom and realized how brightly my neon orange hair stood out but not my red shirt and don’t understand why

In: 3

Answer 1

“Black light” is actually mostly ultraviolet (so invisible to the eye). This is the frequency of light that fluorescent objects can absorb then re-emit some of the energy as visible light.

Since your red shirt is reflecting red light, it is absorbing but not re-emitting UV.