Gramaldi (April 2, 1618 - Dec. 28, 1663) was an Italian mathematician and physicist who studied the diffraction of light. He observed the image on a screen in a darkened room of a tiny beam of sunlight after it passed pass through a fine screen (or a slit, edge of a screen, wire, hair, fabric or bird feather). The image had iridescent fringes, and deviated from a normal geometrical shadow.
He coined the name diffraction for this change of trajectory of the light passing near opaque objects (though, more specifically, it may have been interferences with two close sources that he observed).
This provided evidence for later physicists to support the wave theory of light. With Riccioli, he investigated the object in free fall (1640-50), and found that distance of fall was proportional to the square of the time taken.
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