In this episode of The Dead Scientists, we explore the basics of geometrical optics. Feynman breaks down the simplified model used to understand how light interacts with lenses and mirrors, starting with the concept of a single refracting surface focusing light from one point to another.

We’ll dive into key concepts like focal length—the distance at which parallel rays converge after passing through a lens—and the lens equation, a crucial formula connecting object distance, image distance, and focal length. We also examine magnification, which determines the size ratio between an object and its image, and explore how these principles extend to systems with multiple lenses.

The episode wraps up by addressing the limitations of geometrical optics, including aberrations (image distortions) and resolving power (the ability to distinguish between closely spaced objects). Through clear explanations and intuitive reasoning based on the principle of least time, Feynman guides us through the essential principles of how light behaves in optical systems.

Whether you're a physics enthusiast or curious about how lenses work, this episode provides a comprehensive and accessible exploration of the foundations of geometrical optics.