In layman's terms, the behavior of light as either a wave or a particle depends on the type of experiment or observation being conducted.
When light behaves like a wave, it exhibits characteristics such as interference and diffraction. Interference occurs when two or more waves combine, either reinforcing or canceling each other out, creating patterns of light and dark regions. Diffraction is the bending or spreading out of waves as they pass through an opening or around an obstacle.
For example, when light passes through a narrow slit, it spreads out and creates a pattern of alternating light and dark regions on a screen behind it. This behavior is similar to what we observe when waves, such as water waves or sound waves, pass through a small opening.
On the other hand, light can also behave as a particle, called a photon. Photons are discrete packets of energy that can be thought of as tiny particles. When we interact with light on a smaller scale, such as when we observe individual photons or measure their properties, we see particle-like behavior.
For instance, in certain experiments, when light is directed at a detector, we observe that the light arrives in discrete "chunks" or packets rather than as a continuous wave. This is similar to how particles, such as marbles, would be detected if they were being thrown at a target one by one.
In summary, whether light behaves as a wave or a particle depends on the experiment or observation being conducted. When we observe phenomena like interference and diffraction, light behaves like a wave. However, when we interact with light at a smaller scale, such as measuring individual photons, it exhibits particle-like behavior. This duality between wave and particle behavior is one of the intriguing aspects of quantum physics.