Here's why:

* Wave-like behavior: Light exhibits many wave-like properties. It can diffract (bend around corners), interfere (create patterns of constructive and destructive interference), and exhibit polarization (oscillations in a specific direction).

* Particle-like behavior: Light also interacts with matter like particles. The photoelectric effect, where light knocks electrons off a metal surface, demonstrates that light can transfer energy in discrete packets called photons.

The wave-particle duality: This is a fundamental concept in quantum mechanics, and it applies to light as well as other entities like electrons. It means that light isn't just one or the other; it has both wave-like and particle-like properties, and it's only when we interact with it that we see one aspect or the other.

In short: Light behaves like a wave when it travels through space, and it behaves like a particle when it interacts with matter. It's not a simple choice between particle or wave; it's both, and it's a fundamental property of light that we can't really explain with our everyday intuition.