The physics of optical illusions

Light enables us to see our world around us, but sometimes the light is distorted, modifying how we observe an object. This course will focus on understanding the interactions between light and matter that give rise to these illusions. To first understand how our eyes can be fooled, the course will start by introducing how humans and animals perceive light. It will then go on to understanding the wave- and particle-like nature of light and how these lead to its physical properties.

The light that arrives on Earth from our sun and generated by light bulbs or LEDs generally contains no polarisation, so why can one buy Polaroid glasses and polarising filters for cameras? Polarised light is actually quite commonplace and has been used in many different situations, such as LCD screens and 3D glasses. The course will present what polarised light actually is, how it is generated and used.

The course will then focus on reflection, diffraction, refraction, scattering and interference, which are all interactions between light and matter that arise from the wave-like behaviour of light. These phenomena change the path of the light or induce interactions between multiple light waves to change the appearance of an object. These effects are responsible for the shimmering mirages and the bright colour patterns on soap bubbles and butterfly wings. The course will focus on each interaction in turn, discussing the physics behind it and its modern and not so modern applications.