Bob Haselby and Tony Moss dialoged: > >This sounds like a "signal mirror" ... It uses double internal > >reflection in the hole to give a virtual image of the sun > > Any chance of a diagram or somesuch to show how this works Bob?
It could work like this: Set up two sheets of glass and a mirror so they are all perpendicular to one another. There will be a faint image of the sun reflected in each sheet of glass, but also a still fainter image due to a reflection from both sheets. The direction of this third image is also the direction the sunlight will be reflected from the mirror, so if you tilt the assembly until the faintest image is superimposed on your target, they will see the light. This does not yet sound like a practical piece of emergency equipment, but maybe it will give somebody enough of an idea to figure out how real signal mirrors work. --Art Carlson
