black light

[RichD]

I saw a pocket flashlight in a hardware store yesterday,
it shines UV. Such a package is new to me.

What is it good for? What's inside?

And whence the origin of the term 'black light'?
I recall days gone by, the wall posters were popular, is
that still in fashion?

--
Rich

[Phil Hobbs]

Post by RichD
I saw a pocket flashlight in a hardware store yesterday,
it shines UV. Such a package is new to me.
What is it good for? What's inside?

Probably a 385 nm LED, and used for checking money or something. Folks
also use fluorescent dye for finding leaks, I think. (If they don't,
they should.) ;)

Post by RichD
And whence the origin of the term 'black light'?

Marketing. It's light, but you basically can't see it. The original
ones are just fluorescent tubes with a short-pass filter to pass the
365-nm I-line of mercury. (The more dangerous 254-nm

Post by RichD
I recall days gone by, the wall posters were popular, is
that still in fashion?

I haven't seen one in years, but that doesn't prove anything since I'm
not in fashion anymore either. ;)

Cheers

Phil Hobbs