Timeline/Experiments for Final

Question 1

John Dalton’s Atomic Theory

Answer 1

1803; matter is composed of individual atoms; laid the foundation for modern atomic theory

Question 2

Heinrich Hertz on Photoelectric Effect

Answer 2

1887; demonstrated that ultraviolet light could cause electrons to be emitted from a metal surface; provided experimental evidence for the photoelectric effect and led to quantum theory

Question 3

J.J. Thomson Cathode Ray tube

Answer 3

1897; discovered the electron by observing deflections in cathode rays in electric and magnetic fields; proved that atoms have internal structure, challenging Dalton’s model

Question 4

Max Planck Ultraviolet Catastrophe

Answer 4

1900; proposed that energy is quantized and emitted in packets called quanta (E = hf); resolved the ultraviolet catastrophe by accurately describing blackbody radiation, marked the beginning of quantum mechanics

Question 5

Einstein Publishes on Photoelectric effect

Answer 5

1905; proposed that light is quantized into photons, explaining the photoelectric effect; marked the birth of quantum theory

Question 6

Einstein Publishes Special Relativity

Answer 6

1905; introduced the principles of relativity asserting that the speed of light is constant and unchanging for all observers; revolutionized our understanding of space, time, and energy (E=mc^2)

Question 7

William and Lawrence Bragg Discover X-ray diffraction

Answer 7

1909; showed that x-rays could be diffracted by crystals, revealing their atomic structures; pioneered the field of crystallography and advanced the knowledge of atomic arrangements

Question 8

Millikan’s Oil Drop Experiment

Answer 8

1909-1913; measured the charge of the electron by observing oil droplets in an electric field; provided precise confirmation of the quantized nature of electric charge

Question 9

Rutherford’s Gold Foil Experiment

Answer 9

1911; showed that atoms have dense, positively charged nucleus by observing alpha particle scattering; overturned Thomson’s ‘plum pudding’ model, establishing the nuclear model of the atom

Question 10

Bohr’s Atomic Model

Answer 10

1913; proposed that electrons orbit the nucleus in quantized energy levels, emitting or absorbing energy when transitioning; successfully explain atomic spectra, merging classical and quantum concepts

Question 11

Arthur Compton’s Scattering Experiment

Answer 11

1923; demonstrated the particle nature of photons by showing x-rays scatter with a predictable wavelength shift; confirmed quantum mechanics by proving light has both wave and particle properties

Question 12

Louis de Broglie Publishes on Matter Waves

Answer 12

1924; proposed that particles like electrons have wave properties with wavelengths inversely proportional to momentum; introduced wave-particle duality for matter

Question 13

Davisson-Germer Electron Diffraction Experiment

Answer 13

1927; confirmed de Broglie’s theory by observing electron diffraction patterns on a crystal surface; provided experimental verification of wave-particle duality for matter

Question 14

Dirac Predicts Pair Production

Answer 14

1930; predicted that a photon with enough energy could create an electron-positron pair; theoretically explain how energy could convert into matter and antimatter

Question 15

Anderson’s Observation of the Positron

Answer 15

1933; discovered the positron confirming Dirac’s theory of antimatter; provided direct evidence of antimatter and validated pair production

Question 16

Laboratory observation of pair production

Answer 16

1934; observed pair production by firing high-energy photons at atomic nuclei, creating electron-positron pairs; experimental confirmation of matter-antimatter creation from photon energy