Re: One-way mirror - Another way

[brian whatcott <inet@INTELLISYS.NET>]

At 11:17 4/25/99 -0500, Hasan wrote:
> The window pane should be a dark glass plate of absorptance a.  It can
> be silvered on one side to give reflectance r.....
> -Hasan Fakhruddin
ORTHODOX
Illumination on dark side 1
on bright side  100

50% reflective glass
Bright side:
Reflected  50
transmitted  0.5

Dark side:
Reflected   0.5
transmitted 50

HASAN'S VERSION
Illumination on 'dark' side 100
on bright side  100

50% reflective plus 99% absorptive glass
Bright side:
Reflected: 50
transmitted: 0.5

'Dark' Side:
Reflected: 0.005
transmitted: 0.5

Conclusion: It is possible to provide as great a reduction of transmitted
image from a 'dark' room through a 2 way mirror by providing absorbant
glass rather than reduced illumination of the dark room.
   But the image is much (50 times) brighter than ambient in the dark spy room
compared with much (200 times) dimmer than ambient in the bright spy room
with
dark glass.

Parentheses refer to the example given.

   Better to keep the spies in the dark?

brian whatcott <inet@intellisys.net>
Altus OK