5.3.4

Wave-Particle Duality

Test yourself on Wave-Particle Duality

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Wave-Particle Duality - Light

Interference and diffraction show that light is a wave. The photoelectric effect shows that light must be a particle. Quantum physics means light can be both a wave and a particle at the same time.

Light as a wave

Light as a wave

Experiments such as shining light through a diffraction grating show us that light must be a wave.
Light must diffract through the grating and then interfere constructively and destructively to produce bands of light and dark.
- Only a wave would be able to do this.
- A classical particle (e.g. a tennis ball) cannot interfere with another tennis ball to produce one larger one!

Light as a particle

Light as a particle

The photoelectric effect displays that light must be a particle.
The experiment shows that light particles (photons) have a one-on-one interaction with an electron on the metal surface.

Particle Duality

In 1924, physicist Louis de Broglie suggested that particles might exhibit wave properties, such as diffraction. At the time, scientists dismissed his theory. But electron diffraction and other experiments showed de Broglie was right.

De Broglie wavelength

De Broglie wavelength

De Broglie suggested that any particle with a momentum, mv, must have an associated wavelength, λ, given by:
- $\lambda = \frac{h}{mv}$

$Electron diffraction experiments$

Electron diffraction experiments

After de Broglie came up with this theory, other scientists set up experiments trying to prove (or disprove) his equation.
These experiments showed that electrons did diffract like waves through a grating, and had a wavelength equal to what de Broglie had suggested.
- Given this experimental evidence, scientists changed their minds and accepted de Broglie's theory.

Electron Orbitals

Electrons can exist only in locations where they interfere constructively.

Electron orbits

Electron orbits

How does this affect electrons in atomic orbits?
When an electron is bound to an atom, its wavelength must fit into a small space like a standing wave on a string. - Allowed orbits are those orbits in which an electron constructively interferes with itself.
Not all orbits produce constructive interference.
Only certain orbits are allowed, meaning the orbits are quantized.

Quantization

Quantization

For a circular orbit, the electron waves must fit an integer number of times into the circumference of the orbit:
- $n\lambda_n = 2\pi r_n$
Where λ_n is the electron’s wavelength and r_n is the radius of that circular orbit.

Quantization 2

Quantization 2

Substituting for the de Broglie wavelength of an electron we have:
- $n\frac{h}{m_e \nu}=2\pi r_n$
Substituting for the angular momentum L we can write:
- $L = m_e\nu r_n =n\frac{h}{2\pi} \;(n=1,2,3...)$
So the angular momentum for electrons in orbit must be quantized.

1

Space, Time & Motion

1.1

Motion

1.1.1Motion Basics 1.1.2Graphs of Motion 1.1.3Uniform Acceleration Equations 1.1.4Projectile Motion 1.1.5Bouncing Ball Example

1.2

Forces

1.2.1Friction 1.2.2Terminal Speed 1.2.3Newton's Laws 1.2.4Exam-Style Question - Forces 1.2.5End of Topic Test - Newton's Third Law

1.3

Momentum & Impulse

1.3.1Momentum 1.3.2Momentum 2 1.3.3End of Topic Test - Newton's Laws & Momentum

1.4

Work, Energy & Power

1.4.1Work & Energy 1.4.2Conservation of Energy 1.4.3Power & Efficiency 1.4.4IB Multiple Choice- Work, Energy & Power

2

The Particulate Nature of Matter

2.1

Thermal Concepts

2.1.1Molecular Kinetic Theory Model 2.1.2Molecular Kinetic Theory Model 2 2.1.3Thermal Energy Transfer 2.1.4Thermal Energy Transfer Experiments 2.1.5Thermal Equilibrium 2.1.6Thermal Conductivity 2.1.7Heat Energy Transfer

2.2

Modelling a Gas

2.2.1Ideal Gases 2.2.2Ideal Gases 2 2.2.3End of Topic Test - Thermal Energy & Ideal Gases 2.2.4Exam-Style Question - Ideal Gases

3

Wave Behaviour

3.1

Oscillations

3.1.1Progressive Waves 3.1.2Simple Harmonic Motion

3.2

Travelling Waves

3.2.1Wave Speed & Phase Difference 3.2.2Longitudinal & Transverse Waves 3.2.3Electromagnetic Waves 3.2.4Electromagnetic Waves 2 3.2.5Sound Waves

3.3

Wave Characteristics

3.3.1Polarisation

3.4

Wave Behaviour

3.4.1Reflection & Absorption 3.4.2Reflection of Light 3.4.3Refraction 3.4.4Refractive index

3.5

Standing Waves

3.5.1Standing Waves 3.5.2Standing Waves 2 3.5.3End of Topic Test - Standing Waves 3.5.4IB Multiple Choice - Waves

3.6

Simple Harmonic Motion

3.6.1Simple Harmonic Motion 3.6.2Simple Harmonic Systems 3.6.3Energy in Simple Harmonic Motion 3.6.4End of Topic Test - Simple Harmonic Motion 3.6.5End of Topic Test - Simple Harmonic Motion

3.7

Single Slit Diffraction

3.7.1Diffraction

3.8

Interference

3.8.1Interference 3.8.2Interference 2 3.8.3Diffraction Gratings 3.8.4End of Topic Test - Diffraction

3.9

Doppler Effect

3.9.1Doppler Effect

4

Fields

4.1

Circular Motion

4.1.1Circular Motion 4.1.2Centripetal Force 4.1.3IB Multiple Choice - Circular Motion

4.2

Newton's Law of Gravitation

4.2.1Newton's Law 4.2.2Orbits of Planets & Satellites 4.2.3Escape Velocity & Synchronous Orbits 4.2.4End of Topic Test - Gravitational Fields

4.3

Fields

4.3.1Fields 4.3.2Gravitational Field Strength 4.3.3Gravitational Potential 4.3.4Electric Field Strength 4.3.5Electrostatic & Gravitational Forces 4.3.6Electric Potential 4.3.7IB Multiple Choice - Gravitational Fields

4.4

Fields at Work

4.4.1Radial Field Strength 4.4.2Orbits of Planets & Satellites 4.4.3Escape Velocity & Synchronous Orbits 4.4.4End of Topic Test - Gravitational Fields 4.4.5Uniform Electric Fields 4.4.6IB Multiple Choice - Electric Field & Potential

4.5

Electric Fields

4.5.1Electric Charge 4.5.2Conservation of Charge 4.5.3Coulomb's Law 4.5.4Current 4.5.5Potential Difference 4.5.6IB Multiple Choice - Electric Charge

4.6

Magnetic Effect of Electric Currents

4.6.1Magnetism 4.6.2Magnetic Field 4.6.3Magnetic Force 4.6.4Moving Charges in a Magnetic Field 4.6.5IB Multiple Choice - Magnetism

4.7

Heating Effect of Currents

4.7.1Circuits 4.7.2Resistance 4.7.3Power and Conservation 4.7.4IB Multiple Choice - DC Circuits

4.8

Electromagnetic Induction

4.8.1Electromagnetic Induction 4.8.2Electromagnetic Induction 2 4.8.3Magnetic Flux & Flux Linkage 4.8.4End of Topic Test - Electromagnetic Induction

4.9

Power Generation & Transmission

4.9.1Alternating Currents 4.9.2Operation of a Transformer

4.10

Capacitance

4.10.1Capacitance 4.10.2Parallel Plate Capacitor 4.10.3Energy Stored by a Capacitor 4.10.4Capacitor Discharge 4.10.5Capacitor Charge 4.10.6Magnetic Flux Density 4.10.7End of Topic Test - Capacitance & Flux Density

5

Nuclear & Quantum Physics

5.1

Discrete Energy & Radioactivity

5.1.1Atomic Spectra 5.1.2Atomic Structure 5.1.3Photons 5.1.4Discrete Energy Levels 5.1.5Alpha, Beta & Gamma Radiation 5.1.6Scientific Practices - Unstable Nuclei 5.1.7Radioactive Decay 5.1.8IB Multiple Choice - Atomic Physics

5.2

Nuclear Reactions

5.2.1Mass & Energy 5.2.2Nuclear Fission

5.3

The Interaction of Matter with Radiation

5.3.1Particles, Antiparticles & Photons 5.3.2Particle Interactions 5.3.3Classification of Particles 5.3.4Wave-Particle Duality 5.3.5Wave Functions & Probability 5.3.6IB Multiple Choice - Quantum Physics

5.4

Nuclear Physics

5.4.1Nuclear Instability & Radioactive Decay 5.4.2Nuclear Radius 5.4.3IB Multiple Choice - Nuclear Physics

6

Measurements

6.1

Measurements & Errors

6.1.1Fundamental Units 6.1.2SI Prefixes, Standard Form & Converting Units 6.1.3End of Topic Test - Units & Prefixes

6.2

Uncertainties & Errors

6.2.1Limitation of Physical Measurements 6.2.2Uncertainty 6.2.3Estimation 6.2.4End of Topic Test - Measurements & Errors

6.3

Vectors & Scalars

6.3.1Scalars & Vectors 6.3.2Vector Problems

Jump to other topics

1

Space, Time & Motion

1.1

Motion

1.1.1Motion Basics 1.1.2Graphs of Motion 1.1.3Uniform Acceleration Equations 1.1.4Projectile Motion 1.1.5Bouncing Ball Example

1.2

Forces

1.2.1Friction 1.2.2Terminal Speed 1.2.3Newton's Laws 1.2.4Exam-Style Question - Forces 1.2.5End of Topic Test - Newton's Third Law

1.3

Momentum & Impulse

1.3.1Momentum 1.3.2Momentum 2 1.3.3End of Topic Test - Newton's Laws & Momentum

1.4

Work, Energy & Power

1.4.1Work & Energy 1.4.2Conservation of Energy 1.4.3Power & Efficiency 1.4.4IB Multiple Choice- Work, Energy & Power

2

The Particulate Nature of Matter

2.1

Thermal Concepts

2.1.1Molecular Kinetic Theory Model 2.1.2Molecular Kinetic Theory Model 2 2.1.3Thermal Energy Transfer 2.1.4Thermal Energy Transfer Experiments 2.1.5Thermal Equilibrium 2.1.6Thermal Conductivity 2.1.7Heat Energy Transfer

2.2

Modelling a Gas

2.2.1Ideal Gases 2.2.2Ideal Gases 2 2.2.3End of Topic Test - Thermal Energy & Ideal Gases 2.2.4Exam-Style Question - Ideal Gases

3

Wave Behaviour

3.1

Oscillations

3.1.1Progressive Waves 3.1.2Simple Harmonic Motion

3.2

Travelling Waves

3.2.1Wave Speed & Phase Difference 3.2.2Longitudinal & Transverse Waves 3.2.3Electromagnetic Waves 3.2.4Electromagnetic Waves 2 3.2.5Sound Waves

3.3

Wave Characteristics

3.3.1Polarisation

3.4

Wave Behaviour

3.4.1Reflection & Absorption 3.4.2Reflection of Light 3.4.3Refraction 3.4.4Refractive index

3.5

Standing Waves

3.5.1Standing Waves 3.5.2Standing Waves 2 3.5.3End of Topic Test - Standing Waves 3.5.4IB Multiple Choice - Waves

3.6

Simple Harmonic Motion

3.6.1Simple Harmonic Motion 3.6.2Simple Harmonic Systems 3.6.3Energy in Simple Harmonic Motion 3.6.4End of Topic Test - Simple Harmonic Motion 3.6.5End of Topic Test - Simple Harmonic Motion

3.7

Single Slit Diffraction

3.7.1Diffraction

3.8

Interference

3.8.1Interference 3.8.2Interference 2 3.8.3Diffraction Gratings 3.8.4End of Topic Test - Diffraction

3.9

Doppler Effect

3.9.1Doppler Effect

4

Fields

4.1

Circular Motion

4.1.1Circular Motion 4.1.2Centripetal Force 4.1.3IB Multiple Choice - Circular Motion

4.2

Newton's Law of Gravitation

4.2.1Newton's Law 4.2.2Orbits of Planets & Satellites 4.2.3Escape Velocity & Synchronous Orbits 4.2.4End of Topic Test - Gravitational Fields

4.3

Fields

4.3.1Fields 4.3.2Gravitational Field Strength 4.3.3Gravitational Potential 4.3.4Electric Field Strength 4.3.5Electrostatic & Gravitational Forces 4.3.6Electric Potential 4.3.7IB Multiple Choice - Gravitational Fields

4.4

Fields at Work

4.4.1Radial Field Strength 4.4.2Orbits of Planets & Satellites 4.4.3Escape Velocity & Synchronous Orbits 4.4.4End of Topic Test - Gravitational Fields 4.4.5Uniform Electric Fields 4.4.6IB Multiple Choice - Electric Field & Potential

4.5

Electric Fields

4.5.1Electric Charge 4.5.2Conservation of Charge 4.5.3Coulomb's Law 4.5.4Current 4.5.5Potential Difference 4.5.6IB Multiple Choice - Electric Charge

4.6

Magnetic Effect of Electric Currents

4.6.1Magnetism 4.6.2Magnetic Field 4.6.3Magnetic Force 4.6.4Moving Charges in a Magnetic Field 4.6.5IB Multiple Choice - Magnetism

4.7

Heating Effect of Currents

4.7.1Circuits 4.7.2Resistance 4.7.3Power and Conservation 4.7.4IB Multiple Choice - DC Circuits

4.8

Electromagnetic Induction

4.8.1Electromagnetic Induction 4.8.2Electromagnetic Induction 2 4.8.3Magnetic Flux & Flux Linkage 4.8.4End of Topic Test - Electromagnetic Induction

4.9

Power Generation & Transmission

4.9.1Alternating Currents 4.9.2Operation of a Transformer

4.10

Capacitance

4.10.1Capacitance 4.10.2Parallel Plate Capacitor 4.10.3Energy Stored by a Capacitor 4.10.4Capacitor Discharge 4.10.5Capacitor Charge 4.10.6Magnetic Flux Density 4.10.7End of Topic Test - Capacitance & Flux Density

5

Nuclear & Quantum Physics

5.1

Discrete Energy & Radioactivity

5.1.1Atomic Spectra 5.1.2Atomic Structure 5.1.3Photons 5.1.4Discrete Energy Levels 5.1.5Alpha, Beta & Gamma Radiation 5.1.6Scientific Practices - Unstable Nuclei 5.1.7Radioactive Decay 5.1.8IB Multiple Choice - Atomic Physics

5.2

Nuclear Reactions

5.2.1Mass & Energy 5.2.2Nuclear Fission

5.3

The Interaction of Matter with Radiation

5.3.1Particles, Antiparticles & Photons 5.3.2Particle Interactions 5.3.3Classification of Particles 5.3.4Wave-Particle Duality 5.3.5Wave Functions & Probability 5.3.6IB Multiple Choice - Quantum Physics

5.4

Nuclear Physics

5.4.1Nuclear Instability & Radioactive Decay 5.4.2Nuclear Radius 5.4.3IB Multiple Choice - Nuclear Physics

6

Measurements

6.1

Measurements & Errors

6.1.1Fundamental Units 6.1.2SI Prefixes, Standard Form & Converting Units 6.1.3End of Topic Test - Units & Prefixes

6.2

Uncertainties & Errors

6.2.1Limitation of Physical Measurements 6.2.2Uncertainty 6.2.3Estimation 6.2.4End of Topic Test - Measurements & Errors

6.3

Vectors & Scalars

6.3.1Scalars & Vectors 6.3.2Vector Problems

Practice questions on Wave-Particle Duality

Can you answer these? Test yourself with free interactive practice on Seneca — used by over 10 million students.

1
Which of these statements are true about light?True / false
2
Which of the following is true of particle duality?True / false
3
What kind of waves are formed by electrons in orbit?Multiple choice
4
Which of the following is the correct equation for the angular momentum of an electron in orbit?Multiple choice

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Classification of Particles

Wave Functions & Probability