On Wed, 28 Aug 2019 05:29:07 +0100, Rod Speed wrote:



"Commander Kinsey" wrote in message
news
On Tue, 27 Aug 2019 22:38:57 +0100, Max Demian
wrote:

On 27/08/2019 17:25, Commander Kinsey wrote:
On Tue, 27 Aug 2019 17:13:18 +0100, Colonel Edmund J. Burke
wrote:

On 8/27/2019 9:03 AM, Commander Kinsey wrote:
Why is hi-vis clothing easier to see? What’s so special about the
colour?

Color, you ignorant limey.

So why isn't red, yellow, etc as easy to see? If you wear a bright red
tshirt, you aren't as visible as wearing a hi-vis jacket. Does it
convert all the wavelengths into one or something?

It's fluorescent. It converts ultraviolet (especially prevalent in the
dusk) into visible light.

I never realised this - there's more UV at dusk?

Yep, because the sunlight is going thru a lot more air
and dust etc in the air and UV gets thru that better
than the longer wavelength light. That’s why sunsets
are red, the red light is reflected off the crap in the air.

Isn't it to do with diffraction and refraction?

Or just the same amount, and less visible light?

Less of the long wavelength red end of the spectrum, anyway.

Sunsets are orange.

I guess it's to do with diffraction of sunlight at the horizon?

More the much longer amount of air in the path between
the sun and you.

Presumably mainly available in certain colours.

Why are they always yellow or green?

They arent normally green and plenty are orange/reddish.

Almost every one I see nowadays is yellow. A google image search shows 75% yellow and 25% orange, although I can't remember the last time I saw an orange.

Just to do with the chemicals in the dyes that can convert UV into
visible?

To some extent.

Some, intended to be used at night, have strips that include glass or
plastic beads that reflect light (from torches or car headlamps) back in
the direction the light source is.

I once saw somebody being quite ingenious. He'd broken down
and had no available light source from the vehicle (dead electrics
presumably, no hazard lights etc). He'd put two hi vis jackets on the
back, and every time a car approached, he flashed his torch at them.

Why wasn’t the other car headlights on the hi vis jackets enough ?

Because they weren't shining directly towards them. It was certainly working, I could seer the jackets 5 or 10 times brighter when he used the torch.