Originally Posted by
dougmc
You missed his point.
Reflectors reflect the light back approximately to the source --
that's what they're designed to do, and that's what makes them effective. This
source isn't the driver of the car -- it's the light itself. Now, not
all the light goes right back towards the source -- it spreads out somewhat, and this makes it work when the light isn't right next to your eyes. But as you get closer to the retroreflector, the angle between your light and your eyes increases, and so the effectiveness of the reflector decreases -- THAT is what mechBgon was referring to.
Actually, I do know what he's talking about. This is the so-called observation angle, or how wide the light scatters from the reflector.
Bicycle reflectors are designed to reflect any incoming light back in a cone of about 3 degrees from parallel to the incoming light. If they wouldn't function at a slightly wider angle, they would be very difficult to spot - unless you are shooting laser beams from your eyes!
At about 100 ft a 3 degree angle reaches 6' from parallel, enough to be visible to the driver. This means that even a single facet reflector is visible at 100 ft out, or further, even with one headlight out. If the reflector has more than one facet, another facet will be in better reflective angle (at some point) when the car gets closer than 100 ft.
See the link in my signature for more detailed analysis
