Electromagnetic waves are not visible in themselves but become visible when they are reflected off objects, as the eye detects light that enters through the lens. The detection process involves photoreceptor cells in the retina that respond to visible light, sending signals to the brain to create an image. The eye focuses light from various angles onto different parts of the retina, allowing the brain to interpret distance and location of objects. While light from sources like fluorescent bulbs or the sun can be seen directly, it is often the interaction with other materials that makes it perceptible. Ultimately, light must reach the eye for visibility, and without reflection or refraction, it remains unseen.