Laboratory of Cold Atoms Near Surfaces


Mirror made from a piece of paper

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The reflection of light from a surface (e.g. glass) is described by so called Fresnel equations. We can calculate that about 4% of light is reflected from a piece of glass, when the angle of incidence is close to 0 degrees. More precisely, 4% is reflected from the front surface of a glass, and similary 4% from the back surface. We are used to the fact that the glass works as a mirror. We see it every day in windows or car glass. Depending on the material and the quality of its surface, it reflects the light better or worse.

However, from the Fresnel equations we see that when the angle of incidence is large (close to 900), every material works as a mirror!

Two exemplary methods of observation of this effect are shown below:

schemat lustra z papieru

The “mirror” is made from a common gray ecologic print paper. Image on the left shows the observation of a reflection of light from a lamp whereas right image shows how to observe reflection of objects displayed on a computer screen.

The effect might be observed with a sheet of paper hold in hand, however it is convenient to glue it to a flat stiff surface with a double-face tape. The most important thing to remember is to observe the reflections almost parallel to the surface of a paper sheet, especially in the computer screen version.

Two working examples of a paper mirror are shown below.

Reflection of a lamp:






Reflection of images displayed on a computer screen:



Below the words “dla uczniów” (“for pupils”) one can see their mirror reflection.

The reflection is obviously distorted and weakened due to paper surface roughness.

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(c) Tomasz Kawalec