AY Honors/Optics/Answer Key
The so-called "one-way glass", "two-way mirror" or "mirrored glass" is a technique that exploits the use of an enclosed darkened room and an enclosed well-lit room separated by a pane of highly reflective glass. This is not an ordinary mirror, but something that only appears to be a mirror. This glass is coated with a very thin almost transparent layer of metal to enhance its reflective nature. The result is what appears to be a mirror from one side, and slightly tinted glass from the other. A person on the brightly lit room has difficulty seeing into the darkend room, through what appears to be a mirror.
This is sometimes used for providing security through covert viewing of public spaces like stores from private offices, for protection of covert cameras, and for police interrogation rooms where witnesses can view the proceedings. It has even been used by nefarious landlords to spy on tenants most private spaces. But, it can be detected by the wary.
Other techniques of camoflauge can also be used with ordinary glass, for special effects that make it appear that a ghost sitting next to you or is flying around a room. Such as used in Anaheim California's Disneyland exhibit "Pirates of the Carribean". The effect can also be used in a finely perforated white metal screen, that is difficult to see through in one direction, depending on the relative light levels of the separated spaces.
To take full advantage of the partially mirrored surface to appear like a mirror, one side should be brightly lit, to camoflage any hint of light coming through the glass from the darkened side. The darkened room is only completely secure or non-viewable, when it is completely dark there. Sometimes a darkened curtain or a airlock type vestibule with double doors are used on that side to keep out light. Careful control of the lighting must also be used. Detectives or witnesses on the darkened side should be cautioned not to light a cigarette when close to the glass! Wiley criminals in the examination room, have been known to put their eyes near the glass and cup their hands around their face and peer through. A flashlight held against the glass can also be used to peer through and illuminate the opposite side.
Office workers that work in offices with reflective glass on the outside, should know that their activites, not visible durring the daytime from the outside, are quite visible at night in their well-lit areas.
