Reflective material

[Lou]

aaah, see, now the situation you are thinking of is slightly different to me.  Times when I have been more than aware of reflective coatings are following buddy into dark place, hence getting an eyeful of reflection from my torch (and thanks Dom, I do know what reflection is, even mechanical engineers take their physics that far ;) ).  

Just have to be careful you don't wipe your lovely magnetic strip off on some wreck.....

[Dominic]

Ahh.. I THOUGHT we must be considering different scenarios.

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Originally Posted by [b

Quote[/b] ]and thanks Dom, I do know what reflection is

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Ahh, but DO you? :P I only mentioned the way the panels reflect light in case you were thinking that reflected sunlight, for instance, might be a dazzle problem. - evidently, this wasn't your worry tho.

But technically we're not talking about true reflection: Reflective panels use a specific sub-type known as retroreflection.

Reflected light only goes back the way it came if it hit at 90 degrees to the surface - otherwise it goes in an equal and opposite direction. The reflective panels we're on about actually use retroreflection, which always goes back the way it came.

Score one for the biochemist ;)

(Edited by Dominic at 4:38 pm on Jan. 14, 2003)

[Lou]

But isn't that due to &quot;micropanels&quot; (like faceted strcutures) within the larger panel which *do* use true reflection?

[Dominic]

Interestingly, no.

That's how the solid plastic ones you get on bikes and cars etc work, and apparently it's also the best method, reflecting the highest quantity of light back at the source.

But it only works on rigid structures - so for the panels we get on drysuits and SMBs, it's not possible to use.

Instead, tiny high-refractive-index glass spheres are embedded in a reflective media. If you examine a roadsign or reflective tape or even a car numberplate, you'll just about be able to see that it has a grainy-looking surface due to the tiny, measured-in-microns beads.

And the way it works is:
Light enters glass bead, is refracted to a different angle.
Light hits reflected surface bead is embedded in at 90 degrees
Light is reflected back the way it came
Light is refracted again as it passes back out of the bead

So it's actually a combination of reflection and refraction that makes the whole thing work. Refraction makes sure that no matter where the light comes from, it hits the surface at 90 degrees, and reflection then sends it right back the way it came. This is the opposite of normal reflection, which will send light in the opposite direction to which it came.

Pretty cunning, huh? ;)

(And yes, I DO have a life :tongue2: )

[Lou]

Ah, very interesting. &nbsp;I had noticed the beads but assumed that they were faceted and reflected, rather than spherical and refracted. &nbsp;Dead clever indeed!

Are you quite sure you have a life, though! ;)

[Dominic]

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Originally Posted by [b

Quote[/b] ]Are you quite sure you have a life, though

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Yes.

A person with no life would have discovered this in his spare time.

I found it out when I was at work

[Lou]

Touche! &nbsp;

Point to Mr Humphries.

[Dr Stevil]

got meself sorted with reflective strips for my tanks now. Used the old reflective Sam Brown I mentioned, and two straps which were removed from a Bowstone add-on dive pocket. The reflective material was already fixed to webbing, just threaded the strap thru inbetween the two and added a couple of stitches to hold it securely in place.
Will get a decent test-run if we're doing the Ellerton night dive trip &nbsp;this week
Chee-az
Steve

[Mdemon]

Funnily enough, I've been playing with reflective strips for a while now. &nbsp;Initially I put some luminous mine tape round the valve and end of my cylinder. &nbsp;Works great if everything goes pitch black, but otherwise pretty useless. &nbsp;Got some reflective material of a traffic cone that had taken on a lorry and lost. &nbsp;The material is not very robust, but using transparent outdoor tape, enough is visible on cylinder to respond to a flash of a buddy's torch...

I haven't tried the hood thing, but I probably will. &nbsp;I have seen similar used by soldiers on helmets/hats to make them visible to helicopters, and don't see why it wouldn't work for divers. &nbsp;I suggest some material is on the front of the body too - no good waving yours arms at someone if they can't see them! &nbsp;Perhaps a piece along the edge of a slate might do it - failing that, on the shoulder straps should do.