Final answer:
Louis de Broglie was the physicist who suggested that material particles have wave properties. In his doctoral dissertation, he extended the wave-particle duality of light to material particles, proposing that they exhibit both particle and wave-like behavior.
Step-by-step explanation:
Louis de Broglie suggested that material particles, such as protons, have wave properties as well. In his 1925 doctoral dissertation, de Broglie extended the wave-particle duality of light, which was previously used by Einstein to explain the photoelectric effect, to material particles. He proposed that particles with mass and velocity, like protons, should also exhibit wave-like behavior with a wavelength value given by the expression 2, where h is Planck's constant.