Understand reflection, refraction, lenses and vision.
Understand the concept
Light travels through a uniform medium in straight lines. Reflection returns light to the same medium, while refraction changes its direction when its speed changes between media.
Mirrors and lenses control light rays to form images. These ideas also explain how the human eye focuses light and how corrective lenses help with common vision defects.
Example
Worked example
Calculate refractive index
Light travels at 3 × 10⁸ m/s in vacuum and 2 × 10⁸ m/s in a material. Find the refractive index.