Final answer:
Optical illusions are perceptions where there is a mismatch between an object's appearance and its physical reality. They reveal the fallibility of our perceptual system and can lead to doubts about the accuracy of our senses.
Step-by-step explanation:
Perceptions that involve an apparent discrepancy between how an object looks and what it actually is are known as optical illusions. These phenomena occur when there is a distortion in perception that does not align with the physical reality of the object. Factors such as aberration, accommodation, and the angle of magnification can affect the way objects are perceived. For example, an object viewed through a glass of water appears distorted due to the light bending differently through the glass and water, creating an illusion. The Müller-Lyer illusion is a classic example where lines of the same length appear to be different sizes due to the context in which they are presented.
Optical illusions demonstrate that our perceptual system is not always flawless, and our beliefs about the physical world can sometimes be incorrect. This discrepancy can even lead to philosophical skepticism, challenging the veracity of our perceptions.