What is an optical illusion?

An optical illusion is best described as a perception caused by the way light interacts with objects. This definition highlights the fundamental principle that our visual system interprets light in a certain way, which can sometimes lead us to see something that differs from reality. In optical illusions, the arrangement, color, brightness, and perspective can alter our visual perception, creating effects that may deceive our brains into perceiving something that isn’t there or seeing something in a different way than intended.

For example, certain images may be designed such that they exploit visual cues and contextual information, leading to misinterpretation—like the famous examples of images that look three-dimensional or contain hidden objects despite being flat surfaces. This misinterpretation arises specifically from the complex ways in which light and color can interact with the human visual system. Understanding this aspect of light interaction is key to recognizing how illusions can be created.

In contrast, a visual effect that accurately represents reality would not qualify as an illusion but rather a straightforward depiction of the observed scene. A method to measure light strength pertains to photometry, which is unrelated to the concept of illusions. Similarly, a defect in image formation suggests a flaw, rather than an intentional manipulation of perception as seen in optical illusions. Therefore, the defining characteristic