ExperimentsParticles Behaving as Waves:Waves Behaving as ParticlesSinglephoton/electron double slit experimentThephotoelectric effect1801, Young1905,Einstein1920s, TaylorComptonEffect1974,Merli,Missiroli,Pozz1923, ComptonElectron Diffraction:1925,Davisson and GermerIntroductionandorientationMolecularQuantumMechanics0.1Black-body radiation120.2Heatcapacities0.33The photoelectric andComptoneffects40.4Atomicspectra
Experiments 1801, Young 1920s, Taylor 1974, Merli, Missiroli, Pozz Particles Behaving as Waves: Single photon/electron double slit experiment Electron Diffraction: 1925, Davisson and Germer Waves Behaving as Particles The photoelectric effect 1905, Einstein Compton Effect 1923, Compton Molecular Quantum Mechanics 6
1.1Thewave-particleduality of microscopicparticlesDe BroglieDe Broglie consideredthatthe wave-particlerelationshipinlightis alsoapplicabletoparticlesofmatter,i.eh=Planck'sconstant,E=-hvp = particle momentum,p=h/Λ入=deBrogliewavelength1929Thewavelengthofaparticlecouldbe determined by=h/p=h/mvIntroduction andorlentation10.1Black-bodyradiation20.2Heat capacities30.3ThephotoelectricandComptoneffects40.4Atomicspectra50.5Theduality ofmatter
1.1 The wave-particle duality of microscopic particles De Broglie 1929 De Broglie considered that the wave-particle relationship in light is also applicable to particles of matter, i.e. E=h p=h/ h = Planck’s constant, p = particle momentum, = de Broglie wavelength The wavelength of a particle could be determined by = h/p = h/mv 7
ThedeBroglieWavelengthsof SeveralparticlesParticlesMass (g)入(m)Speed (m/s)9 × 10-281.07 × 10-4Slowelectron9×10-281 × 10-105.9 × 106Fastelectron6.6 × 10-247 × 10-151.5 ×107Alphaparticle7 × 10-291.00.01One-gram mass2 × 10 -3414225.0Baseball4 × 10 -636.0 × 10273.0×104Earth
The de Broglie Wavelengths of Several particles Particles Mass (g) Speed (m/s) (m) Slow electron 9 10 - 28 1.0 7 10 -4 Fast electron 9 10 - 28 5.9 106 1 10 -10 Alpha particle 6.6 10 - 24 1.5 107 7 10 -15 One-gram mass 1.0 0.01 7 10 - 29 Baseball 142 25.0 2 10 - 34 Earth 6.0 1027 3.0 104 4 10 - 63 8
The wave-particle duality. Wave (i.e., light)- can be wave-like (diffraction)-canbeparticle-like(p-h/2).Particles- can be wave-like (2 =h/p)- can be particle-like (classical)Wave-particle duality is the concept that every particle may be partly described in termsnot only of particles, but also of waves. It expresses the inability of the classical concepts'particle"or"wave"tofully describethe behaviour of quantum-scale objects.Becauseparticles sometimes behave like waves or exhibit waveproperties, its hard to measurelocationsandvelocitieswithprecision
The wave-particle duality • Wave (i.e., light) - can be wave-like (diffraction) - can be particle-like (p=h/) • Particles - can be wave-like ( =h/p) - can be particle-like (classical) Wave–particle duality is the concept that every particle may be partly described in terms not only of particles, but also of waves. It expresses the inability of the classical concepts "particle" or "wave" to fully describe the behaviour of quantum-scale objects. Because particles sometimes behave like waves or exhibit wave properties, its hard to measure locations and velocities with precision. 9
TheUncertaintyPrincipleHeisenberg'sinsightBohr,Heisenberg,Pauli(LtoR)hAxApz4元The more precisely the position is determined, the lesspreciselythemomentumisknowninthisinstant,andvice versa.--Heisenberg, uncertainty paper,1927·Classical: the error in the measurement depends on the precision of the apparatus, could bearbitrarily small..Quantum: it is physically impossible to measure simultaneously the exact position and theexactvelocityofaparticleThe description of the behavior of electrons in atoms requires a completely new quantumtheory
•Classical: the error in the measurement depends on the precision of the apparatus, could be arbitrarily small. •Quantum: it is physically impossible to measure simultaneously the exact position and the exact velocity of a particle. The description of the behavior of electrons in atoms requires a completely new “quantum theory”. The Uncertainty Principle 4 h x p 10