Diffraction of light was discovered by A. YoungB. HertzC. GrimaldiD. Malus

The phenomenon of diffraction, which is the bending and spreading of light waves around obstacles and openings, was first observed and named by Francesco Maria Grimaldi, an Italian physicist and Jesuit priest.

In the mid-17th century, Grimaldi conducted experiments where he observed that light does not always travel in straight lines. Instead, when it passes through small apertures or edges, it spreads out—a behavior contrary to the then-accepted laws of geometric optics. He meticulously documented these observations in his work titled "Physico-mathesis de lumine, coloribus, et iride," published in 1665. In this work, he introduced the term "diffraction" to describe this phenomenon.

While Thomas Young later provided significant contributions to the wave theory of light through his famous double-slit experiment, and Étienne-Louis Malus discovered the polarization of light by reflection, the initial discovery and naming of diffraction are attributed to Grimaldi. Heinrich Hertz, on the other hand, is renowned for his work on electromagnetic waves but not directly related to the discovery of light diffraction.

Correct Answer: C. Grimaldi