How can light show both wave-like and particle-like behavior?

Light exhibits both wave-like and particle-like behavior due to a phenomenon known as wave-particle duality. This concept suggests that light is not exclusively one or the other, but possesses characteristics of both depending on the physical context.12

Wave-like Behavior

The wave nature of light is evidenced by phenomena such as interference, where overlapping light waves create distinct patterns. This behavior is well-described by classical electromagnetic wave theory, which treats light as a continuous, nonlocalized wave phenomenon.32

Particle-like Behavior

Conversely, the photoelectric effect demonstrates that light interacts with matter as discrete packets of energy called photons. When light strikes a surface, it can eject electrons only if the individual photons possess sufficient energy, which is determined by the light's frequency rather than its intensity. This particle-like interaction, first explained by Albert Einstein in 1905, confirms that light is localized in these energy packets.451

In modern physics, these two aspects are understood through the complementarity principle, which recognizes that wave and particle descriptions are complementary ways of understanding the same phenomenon.12