Historical Timeline — Dual Nature of Radiation & Matter
| Year | Scientist(s) | Discovery / Contribution |
|---|---|---|
| 1887 | Heinrich Hertz | First observed photoelectric effect during experiments on EM waves; noticed sparks were enhanced by UV light |
| 1888 | Wilhelm Hallwachs | Showed zinc plate loses negative charge when illuminated by UV; positive charges not affected |
| 1900 | Max Planck | Proposed energy quantisation: E = hν to explain blackbody radiation; introduced Planck's constant h |
| 1902 | Philipp Lenard | Systematic photoelectric experiments; showed depends on frequency, NOT intensity; won Nobel 1905 |
| 1905 | Albert Einstein | Explained photoelectric effect using photon concept: = hν − φ; extended Planck's quanta to light itself; Nobel Prize 1921 |
| 1916 | Robert Millikan | Precise measurements of h from photoelectric experiments; confirmed Einstein's equation and measured h = J·s; Nobel 1923 |
| 1923 | Arthur Compton | Demonstrated photon momentum (p = h/λ) via X-ray scattering from electrons (Compton effect); Nobel 1927 |
| 1924 | Louis de Broglie | Proposed matter waves: λ = for all particles; extended wave-particle duality to matter; Nobel 1929 |
| 1927 | Clinton Davisson & Lester Germer | Observed electron diffraction from Ni crystal; confirmed de Broglie's hypothesis; Davisson Nobel 1937 |
| 1928 | George Paget Thomson | Independently confirmed electron diffraction using thin metal foils; Nobel 1937 (shared with Davisson) |