an historical review of natural phenomena and models that demonstrates wave-particle duality

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An Historical Review An Historical Review of Natural Phenomena and of Natural Phenomena and

ModelsModels

That DemonstratesThat Demonstrates

Wave-Particle DualityWave-Particle Duality

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Reflection and RefractionReflection and Refraction

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

The PhenomenonThe Phenomenon

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Light rays consist of particles that obey the Light rays consist of particles that obey the laws of classical mechanics.laws of classical mechanics.

Hugens, ~ 1650Hugens, ~ 1650

Newton, ~ 1650Newton, ~ 1650

Light rays consist of pinpoint wave sources. Light rays consist of pinpoint wave sources. The direction of the wave front determines The direction of the wave front determines the direction of the ray. the direction of the ray.

The ModelThe Model

Reflection and RefractionReflection and Refraction

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Fresnel ~ 1800Fresnel ~ 1800

Light can “circumvent” obstacles and Light can “circumvent” obstacles and illuminate regions that should have illuminate regions that should have been shadowed been shadowed (according to the laws of (according to the laws of Geometrical Optics)Geometrical Optics)

CircumventionCircumvention


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Young ~ 1800Young ~ 1800

InterferenceInterference

Light passing through two slits Light passing through two slits ((dd1mm)1mm) displays a pattern of displays a pattern of alternating dark and light stripes on a alternating dark and light stripes on a screen placed in front of these two screen placed in front of these two slits.slits.

<d><d>


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Circumvention and Interference Circumvention and Interference

1.1. Light consists of waves, which are Light consists of waves, which are periodic functionsperiodic functions

2.2. The superposition of two waves is also a The superposition of two waves is also a wave functionwave function

3.3. The light intensity is proportional to the The light intensity is proportional to the square amplitude of the wave function square amplitude of the wave function

sin sin = m = m / d / d

The ModelThe Model

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Diffraction GratingDiffraction Grating

A light ray passing through A light ray passing through a ruled slide a ruled slide (d (d 1µ) 1µ) splits into a splits into a number of raysnumber of rays

The ModelThe Model

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A constructive interference occurs A constructive interference occurs into specific directions. The into specific directions. The difference in optical paths for the difference in optical paths for the rays coming from each slit is an rays coming from each slit is an integer multiple of the wavelength.integer multiple of the wavelength.

d sin d sin = m = m

Diffraction GratingDiffraction Grating

The ModelThe Model

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Electromagnetic RadiationElectromagnetic Radiation

An electric current alternating An electric current alternating within a conductor produces a within a conductor produces a radio-wave propagating at the radio-wave propagating at the speed of lightspeed of light

Light is an electromagnetic Light is an electromagnetic wavewave

Hertz 1888Hertz 1888 Maxwell 1864Maxwell 1864

The PhenomenonThe Phenomenon The ModelThe Model

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The Photoelectric EffectThe Photoelectric Effect

A surface of metal illuminated by A surface of metal illuminated by light ejects electrons. The kinetic light ejects electrons. The kinetic energy of the electrons is energy of the electrons is proportional to the frequency of the proportional to the frequency of the impinging light. impinging light.

Light is composed of particles Light is composed of particles whose energy is:whose energy is:

Mulliken 1916Mulliken 1916 Einstein 1905Einstein 1905


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The Compton EffectThe Compton Effect

Compton 1923Compton 1923

A laser ray, directed opposite to A laser ray, directed opposite to the flow of a beam of hot sodium the flow of a beam of hot sodium atoms, cools the atoms. This atoms, cools the atoms. This occurs due to momentum transfer occurs due to momentum transfer from the light to the moving atoms.from the light to the moving atoms.

Light is composed of particles Light is composed of particles with the following momentum:with the following momentum:


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Cathode RadiationCathode Radiation

Thomson 1897Thomson 1897 The rays are composed of particles The rays are composed of particles having a negative mass and chargehaving a negative mass and chargeCathode rays are deflected off their Cathode rays are deflected off their

pathway by magnetic and electric pathway by magnetic and electric fieldsfields


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Mulliken 1913Mulliken 1913

The Oil Drop ExperimentThe Oil Drop Experiment

Sprayed oil droplets become Sprayed oil droplets become electrically charged by an integer electrically charged by an integer multiple of a value ‘e’ chargemultiple of a value ‘e’ charge

The charge stems from particles, The charge stems from particles, of which each is charged by the of which each is charged by the elementary charge ‘e’ elementary charge ‘e’


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The De Broglie WaveThe De Broglie Wave

De Broglie 1924De Broglie 1924Particles can possess a wave-like Particles can possess a wave-like behavior. The particles’ behavior is behavior. The particles’ behavior is analogous to light when it behaves analogous to light when it behaves like a particle. like a particle.

The wavelength corresponding The wavelength corresponding to a particle of mass ‘m’ and to a particle of mass ‘m’ and velocity ‘v’ is:velocity ‘v’ is:

TheThe ModelModel

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Davison-Gremer 1927Davison-Gremer 1927When a beam of electrons, When a beam of electrons, accelerated in a low electric field, accelerated in a low electric field, hits a Ni crystal, it creates a hits a Ni crystal, it creates a diffraction pattern.diffraction pattern.

Diffraction of Electrons from a CrystalDiffraction of Electrons from a Crystal


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Diffraction of Electrons from a CrystalDiffraction of Electrons from a Crystal

Electrons are waves with a Electrons are waves with a wavelengthwavelength

The three directions of the crystal The three directions of the crystal create three intersecting diffraction create three intersecting diffraction patternspatterns

The ModelThe Model

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Diffraction of Atoms from a CrystalDiffraction of Atoms from a Crystal

A beam of particles (He, HA beam of particles (He, H22) ) hitting a LiF crystal splits into hitting a LiF crystal splits into several rays.several rays.

2020oo 15 15o o 1010o o 55o o 00o o 55o o 1010o o 1515o o 2020o o

He 100He 100ooKK

He 300He 300ooKK

Stern 1930Stern 1930


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Atom Diffraction from a CrystalAtom Diffraction from a Crystal

A supersonic beam of He particles hitting a GaAs crystal splits A supersonic beam of He particles hitting a GaAs crystal splits into numerous raysinto numerous rays


an historical review of natural phenomena and models that demonstrates wave-particle duality

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