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How do reflection and refraction result from electromagnetic radiation interacting with matter?

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Diagram of a tree leaf illustrating photosynthesis, with arrows showing sunlight, water, and carbon dioxide entering the leaf and sugars and oxygen being produced. A person is shown beside the tree to demonstrate the exchange of oxygen and carbon dioxide between plants and animals. — electromagnetic radiation Diagram of photosynthesis showing how water, light, and carbon dioxide are absorbed by a plant to produce oxygen, sugars, and more carbon dioxide.

When electromagnetic radiation interacts with matter, reflection and refraction arise from the collective behavior of charged particles within the material.

The Role of Charge Oscillators

Matter contains a vast number of charged particles, such as electrons, which act as charge oscillators. When an electromagnetic wave strikes a material, its electric field forces these oscillators to move in unison, following the frequency of the incoming wave. As these charges accelerate, they emit secondary electromagnetic radiation.1

Reflection and Refraction

The total secondary radiation produced by these coherent oscillators results in two primary phenomena:

Reflection: A portion of the secondary radiation is emitted back away from the surface of the material, which we perceive as reflection.1
Refraction: Another portion of the secondary radiation propagates into the material. Refraction occurs because the wave's speed changes as it passes from one medium to another. This change in speed causes the wave to bend, or change direction, as it crosses the boundary.21

The degree of this bending, or refraction, is determined by the material's refractive index, which can vary based on the frequency of the radiation—a phenomenon known as dispersion.3