Fraunhofer diffraction - Bending light rays with your ears
In optics, Fraunhofer diffraction is a type of wave diffraction which occurs when field waves are passed through an aperture or slit, causing the size of an observed aperture image to change due to the far-field location of observation and the increasingly planar nature of outgoing diffracted waves passing through the aperture.
In the image above, the vertical blinds in a window form slits which bend the rays of the sun and influence the shapes of the shadows projected on the wall. The vertical blind acts like a diffraction grating with a set of parallel slits. As the ears approach the shadows of the vertical blinds, the shadow of the ears stretches toward the shadow of the vertical blind to produce elongated ear shadows.
Fraunhofer diffraction is named after the German physicist Joseph von Fraunhofer (1787-1826), the inventor of the diffraction grating. Fraunhofer started the field of stellar spectroscopy and transformed it into a quantitative science by measuring the wavelength of light accurately. He discovered the absorption lines in the optical spectrum of the Sun which are named after him. The Fraunhofer absorption lines can be used to determine the chemical composition in the upper layers of the Sun and the stars because each chemical element absorbs light at specific frequencies.
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