The interaction of light with a medium changes all the characteristics of light, including but not limited to the direction of light transmission, the phase of light, the amplitude of light, the frequency of light, the wavelength of light, the speed of light and so on. However, people's understanding of what light really is is still not completely unified, there are those who think light is electromagnetic wave, there are those who think light is photon, and there are those who think light has wave-particle two-phase nature. Through my long time research found: from the existence of reflected light half-wave loss, polarization refraction light Faraday magneto-optical effect, single-slit diffraction light intensity change four laws, double-slit interference phenomenon, Seeman effect, medium surface state determines the phenomenon of absorbance, the speed of light at the interface of different media jump and uniform medium internal speed of light relative to the medium itself speed constant and other phenomena after comprehensive analysis can be concluded: light is neither electromagnetic waves, nor photons, and there is no wave-particle duality. Light should only be one of the manifestations of the Coulombic and magnetic interactions between charges, and cannot be an object that can exist independently of the charge/light source. In this paper, we focus on the relevant issues with the chain of evidence formed by many evidences of the law of light-medium interaction, with a view to correcting the current misconceptions about the nature of light. Also, the results of several light-related physical experiments, such as the Michelson-Morley experiment, the photoelectric effect and the Compton effect, are explained in terms of the light-dielectric interaction law.