Wave theory provides a framework to understand the propagation of light through a medium. According to this theory, light is an electromagnetic wave that consists of oscillating electric and magnetic fields. As light interacts with a medium, several phenomena occur, including absorption, transmission, reflection, and refraction.
When light passes through a medium, such as air, water, or glass, it encounters atoms or molecules that make up the material. The electric field of the light wave interacts with these charged particles, causing them to oscillate. As a result, the charged particles re-emit the absorbed energy in all directions, including backscattering and forward propagation.
The collective effect of these interactions leads to the attenuation or absorption of light within the medium. The amount of absorption depends on the properties of the material and the frequency of the light. In some cases, the absorbed energy is quickly re-emitted as light, resulting in transparent or transmitting media. In other cases, the absorbed energy is re-emitted in various directions, leading to scattering or reflection.
When light encounters the boundary between two different media, such as air and glass, the change in the refractive index at the interface causes the light to change direction. This phenomenon is known as refraction. The change in direction is a consequence of the wave nature of light and can be described by Snell's law, which relates the angle of incidence and the angle of refraction.
In summary, wave theory explains how light interacts with a medium by considering the oscillation of electric and magnetic fields and the interactions of these fields with charged particles in the material. This theory accounts for phenomena such as absorption, transmission, reflection, and refraction that occur as light propagates through different media.