The behavior of light as both a wave and a particle is a fundamental concept in quantum mechanics, known as wave-particle duality. It can be somewhat counterintuitive but has been well-established through experimental observations.
When light passes through a camera lens, it behaves primarily as a wave. The lens refracts or bends the light waves, focusing them onto the camera's sensor. This is similar to how a lens in a telescope or eyeglasses works. The wave nature of light is evident in phenomena like diffraction and interference patterns, which can be observed when light passes through narrow slits or encounters obstacles.
On the other hand, when light hits the sensor of a digital camera, it interacts with the individual light-sensitive elements (pixels) on the sensor surface. At this scale, light behaves more like particles called photons. Each photon carries a discrete amount of energy and momentum. When a photon strikes a pixel on the sensor, it can be absorbed by the sensor material, creating an electrical signal that can be recorded and processed to form an image.
The transition from wave-like behavior to particle-like behavior occurs because the interaction between light and matter happens at a smaller scale, where quantum mechanics becomes relevant. At the level of individual photons and pixels, the discrete nature of light becomes apparent. However, it's important to note that even in the particle-like description, the statistical behavior of many photons still exhibits wave-like properties, such as interference and diffraction, which can be observed in certain experiments.
In summary, the wave-particle duality of light is a fundamental aspect of quantum mechanics, and depending on the specific circumstances and scales involved, light can exhibit both wave-like and particle-like behavior.