Part II — Chapter 6
Optics & the Nature of Light
The centuries-long debate over whether light is a wave or a particle
6.1 Newton's Prism
Newton demonstrated in 1666 that white light is a mixture of colors using a prism. His Opticks (1704) proposed a corpuscular theory — that light consists of tiny particles.
6.2 Huygens and the Wave Theory
Christiaan Huygens (1629–1695) proposed that light is a wave, explaining reflection and refraction. For a century, Newton's prestige kept the corpuscular theory dominant.
6.3 Young and Fresnel
In 1801, Thomas Young's double-slit experiment demonstrated light interference, proving wave behavior. Augustin Fresnel developed a rigorous wave theory. The debate would only be resolved in the 20th century by quantum mechanics: light is both.