Visual phenomena refer to various visual effects or illusions that occur when light interacts with objects or when our brain processes visual information. These phenomena can include optical illusions, where our perception differs from reality, such as the Müller-Lyer illusion, where lines of equal length appear different due to arrow-like ends. Another example is afterimages, which occur when we stare at a bright image and then look away, causing a lingering impression of the image in complementary colors. Visual phenomena can also involve natural occurrences, like rainbows, which result from the refraction and dispersion of light in water droplets.