# 1 An Historical Review of Natural Phenomena and Models of Natural Phenomena and Models That Demonstrates Wave-Particle Duality.

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1 An Historical Review of Natural Phenomena and Models of Natural Phenomena and Models That Demonstrates Wave-Particle Duality

2 Reflection and Refraction Light waves passing through one transparent medium into another are partly reflected and partly transmitted. There is a constant ratio between the angles at which the rays are hitting, reflecting, and passing. The Phenomenon

3 Light rays consist of particles that obey the laws of classical mechanics. Hugens, ~ 1650 Newton, ~ 1650 Light rays consist of pinpoint wave sources. The direction of the wave front determines the direction of the ray. The Model Reflection and Refraction

4 Fresnel ~ 1800 Light can “circumvent” obstacles and illuminate regions that should have been shadowed (according to the laws of Geometrical Optics) Circumvention The Phenomenon

5 Young ~ 1800 Interference Light passing through two slits (d  1mm) displays a pattern of alternating dark and light stripes on a screen placed in front of these two slits. The Phenomenon

6 Circumvention and Interference 1. Light consists of waves, which are periodic functions 2. The superposition of two waves is also a wave function 3. The light intensity is proportional to the square amplitude of the wave function sin  = m / d The Model

7 Diffraction Grating A light ray passing through a ruled slide (d  1µ) splits into a number of rays The Model

8 A constructive interference occurs into specific directions. The difference in optical paths for the rays coming from each slit is an integer multiple of the wavelength. d sin  = m d sin  = m Diffraction Grating   The Model

9 Electromagnetic Radiation An electric current alternating within a conductor produces a radio-wave propagating at the speed of light Light is an electromagnetic wave Hertz 1888 Maxwell 1864 The Phenomenon The Model

10 The Photoelectric Effect A surface of metal illuminated by light ejects electrons. The kinetic energy of the electrons is proportional to the frequency of the impinging light. Light is composed of particles whose energy is: Mulliken 1916 Einstein 1905 The Phenomenon The Model

11 The Compton Effect Compton 1923 A laser ray, directed opposite to the flow of a beam of hot sodium atoms, cools the atoms. This occurs due to momentum transfer from the light to the moving atoms. Light is composed of particles with the following momentum: The Phenomenon The Model

12 Cathode Radiation Thomson 1897 The rays are composed of particles having a negative mass and charge Cathode rays are deflected off their pathway by magnetic and electric fields The Phenomenon The Model

13 Mulliken 1913 The Oil Drop Experiment Sprayed oil droplets become electrically charged by an integer multiple of a value ‘e’ charge The charge stems from particles, of which each is charged by the elementary charge ‘e’ The Phenomenon The Model

14 The De Broglie Wave De Broglie 1924 Particles can possess a wave-like behavior. The particles’ behavior is analogous to light when it behaves like a particle. The wavelength corresponding to a particle of mass ‘m’ and velocity ‘v’ is: The Model

15 Davison-Gremer 1927 When a beam of electrons, accelerated in a low electric field, hits a Ni crystal, it creates a diffraction pattern. Diffraction of Electrons from a Crystal The Phenomenon

16 Diffraction of Electrons from a Crystal Electrons are waves with a wavelength The three directions of the crystal create three intersecting diffraction patterns The Model

17 Diffraction of Atoms from a Crystal A beam of particles (He, H 2 ) hitting a LiF crystal splits into several rays. 20 o 15 o 10 o 5 o 0 o 5 o 10 o 15 o 20 o He 100 o K He 300 o K Stern 1930 The Phenomenon

18 Atom Diffraction from a Crystal A supersonic beam of He particles hitting a GaAs crystal splits into numerous rays The Phenomenon

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