Knives, forks, and spoons made from a biodegradable starch-polyester material.
<p>The photo has been realized using the photoelasticity method, an experimental
method which gets a fairly accurate picture of stress distribution even around 
abrupt discontinuities in a material.
</p><p>When a ray of plane polarised light is passed through a photoelastic material, it gets
resolved along the two principal stress directions and each of these components experiences 
different refractive indices. The difference in the refractive indices leads to a relative 
phase retardation between the two component waves.
</p><p>The setup used to photograph this photo was probably composed of:
</p>
<ul><li>A regular light source, with a quarter-wave plate installed to polarize the emerging light</li>
<li>A regular photo camera, with a quarter-wave plate installed in front of the lens</li></ul><p>Light and camera being installed and oriented in the same direction, the two
</p>
quarter-wave plates were turned with the polarizing axis in the same direction.
Scott Bauer
Unknown date<div style="display: none;">Unknown date</div>
This image was released by the <a href="https://en.wikipedia.org/wiki/Agricultural_Research_Service" class="extiw" title="en:Agricultural Research Service">Agricultural Research Service</a>, the research agency of the <a href="https://en.wikipedia.org/wiki/United_States_Department_of_Agriculture" class="extiw" title="en:United States Department of Agriculture">United States Department of Agriculture</a>, with the ID <a rel="nofollow" class="external text" href="https://www.ars.usda.gov/is/graphics/photos/k7245-1.htm">k7245-1</a> <a class="external text" href="https://commons.wikimedia.org/w/index.php?title=Category:Media_created_by_the_United_States_Agricultural_Research_Service_with_known_IDs&amp;filefrom=k7245-1#mw-category-media"><small>(next)</small></a>.