If you photocopy a black sheet of paper, it comes out black. If you photocopy a white sheet of paper, it comes out white. But, interestingly, if you put a mirror face down on a photocopier is comes out black. Why?
This is fun! I have got to try first! Are we talking about a old fashioned black and white photocopier or a colored one? :)
The type of photocopier shouldn't matter, I don't think. What I believe is happening is that the light source is placed so that its image beneath the mirror sits outside the sensor's field of view.
This is why you don't get a big white mess when scanning photographs or other glossy papers. See the attachment for a moderately crude diagram.
Someone has posted online a scan of a mirror, demonstrating how you can see the scratches:
http://www.flickr.com/photos/sxenko/496942265/
They came to a similar conclusion, that the reflection was suppressed because of the distance between the light source and sensor.
the entire output will be BLACK because photocopy machine generates the result after the reflection of light to the white portion of the original copy , sir in your case if mirror is placed whole light will reflect back that result as a totally black print .
process of photocopy is
A bright lamp illuminates the original document, and the white areas of the original document reflect the light onto the surface of the photoconductive drum. The areas of the drum that are exposed to light become conductive and therefore discharge to the ground. The area of the drum not exposed to light (those areas that correspond to black portions of the original document) remain negatively charged. The result is a latent electrical image on the surface of the drum
Derek, this seems to be a more intriguing question than first meets the eye and one that probably does not have a straight answer. It relates to the general problems of imagery where opaqueness, reflectivity and specularity needs to be considered. In particular, as I understand it, specularity needs to be defined as the roughness of the surface affecting scattering angles of reflected light. (It seems like this is somewhat confused in in modern use of the concept in 3D graphics).
An ideal mirror has perfect reflectivity, no specularity and no opaqueness. Moost copying machines are designed for materials that can be more or less opaque, high specularity and fairly low reflectivity. I can see at least 3 possible outcomes for the mirror experiment, depending on the design of the copying machine. As mentioned previously, usually the light source and the detector are out of line giving You black as a result. If the detector and light source are inline the image would be a saturated white. If the detector is a ccd camera, the image would be a slightly out of focus image of the camera (Assuming diffuse illumination).
A variation of the question could be how the image of reflecting spheres as in paint on reflecting road signs would look like? Interesting if not entirely legal experiment...
A perfect mirror doesn't scatter so you don't get any light on the drum. Defects in the mirror do scatter hence you get light on the drum
This may depend on the type of copier. If a plane wave of light hits a piece of paper, it reflects off in all directions. If it hits a mirror, it reflects off at only one angle, the specular reflection angle which satisfies angle of incidence equals the angle of reflection. If the light detector in the copier is not located so that the specular reflection angle is collected by it, then a mirror will appear black.
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