What phenomenon is explained by a camera obscura?

A camera obscura is a simple device that demonstrates the principles of image formation via light. It consists of a darkened room or box with a small aperture (or pinhole) on one side. When light passes through this pinhole, it projects an inverted image of the outside scene onto the opposite wall inside the box. This phenomenon illustrates how light travels in straight lines and the way images can be formed by light entering through a small opening.

The process of pinhole image formation relies on the fundamental principles of optics. The smaller the aperture, the sharper the image appears, although less light enters, which can lead to a dimmer image. This demonstrates fundamental concepts of geometry and light behavior, making it a prime example of how a camera obscura works.

The other options are related to different aspects of physics and optical science, but they do not pertain to the specific operation of a camera obscura. For instance, color perception relates to how humans interpret various wavelengths of light, sound reflection deals with how sound waves bounce off surfaces, and light diffusion involves the scattering of light as it passes through or reflects off different materials.