Romer observed the eclipses of Jupiter's moon Io and noticed discrepancies in their timing. He concluded that light has a finite speed and calculated its approximate value.

Impact: This was the first quantitative evidence that light does not travel instantaneously, laying the groundwork for future studies on the nature of light

Scientist(s): Christiaan Huygens

Description: Huygens published his mathematical wave theory of light, suggesting that light propagates as waves through a medium called the "luminiferous ether."

Impact: This theory explained phenomena like reflection and refraction and became a cornerstone of the wave theory of light

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Opticks, Newton proposed that light is composed of particles (or "corpuscles") that travel in straight lines. He used this theory to explain reflection and refraction.

Young demonstrated that light passing through two slits produces an interference pattern, a hallmark of wave behavior.

Einstein explained the photoelectric effect by proposing that light is made of discrete packets of energy called photons, which behave like particles.

This discovery introduced the concept of wave-particle duality and earned Einstein the Nobel Prize in Physics in 1921

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De Broglie proposed that particles, such as electrons, also exhibit wave-like properties, extending the concept of wave-particle duality to matter. This idea was foundational to quantum mechanics and changed the way scientists understood the behavior of light and matter

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This experiment demonstrated the diffraction of electrons, confirming de Broglie's hypothesis that particles can exhibit wave-like behavior.

Impact: It provided experimental evidence for wave-particle duality and further supported quantum mechanics.