https://phys.org/news/2018-06-illuminates-quantum-magnets-mimic.html

Ever since Isaac Newton refracted light through prisms in 1672, scientists have been split over whether light is made up of particles or waves. Light seems to travel in straight lines, as would be expected of a particle, but Newton's experiments have shown it also has frequency and wavelength, like sound waves.

Almost 200 years later, the Scottish physicist James Clerk Maxwell supplied one part of the answer, when he realized that light was made up of fluctuating electric and magnetic fields. It was only in the 20thcentury through the work of Einstein, that light was finally understood to be made up of fundamental particles called photons, which act like both particles and waves.