Photoelectric effect equation

General physics

Basic Principles of Quantum Physics — Physics Lesson

🎯 Learning Objectives

Learning Objectives

Understand the basic principles of quantum physics, including wave-particle duality and quantization of energy
Explore key phenomena such as the photoelectric effect and quantum tunneling
Apply quantum principles to solve problems in atomic and molecular physics
Analyze the historical development of quantum theory from classical physics
Explain the significance of Planck’s constant and its role in quantum mechanics
Describe the uncertainty principle and its implications for measurement
Understand quantum energy levels in atoms and their relationship to spectral lines

🗣️ Language Objectives

Language Objectives

Use precise scientific terminology to describe quantum phenomena and principles
Explain complex quantum concepts using appropriate technical vocabulary
Describe wave-particle duality and its experimental evidence clearly
Communicate the probabilistic nature of quantum mechanics effectively
Express mathematical relationships in quantum physics systematically
Discuss the philosophical implications of quantum theory using scientific language
Compare and contrast classical and quantum physics concepts accurately

📝 Key Terms

Key Terms

English Term	Russian Translation	Kazakh Translation
Quantum Physics	Квантовая физика	Кванттық физика
Wave-Particle Duality	Корпускулярно-волновой дуализм	Толқын-бөлшек қосарланғандығы
Quantization	Квантование	Кванттау
Photoelectric Effect	Фотоэлектрический эффект	Фотоэлектрлік эффект
Quantum Tunneling	Квантовое туннелирование	Кванттық туннельдеу
Planck’s Constant	Постоянная Планка	Планк тұрақтысы
Uncertainty Principle	Принцип неопределенности	Белгісіздік принципі
Energy Levels	Энергетические уровни	Энергетикалық деңгейлер

🃏 Topic Flashcards

Interactive Flashcards

Practice with these flashcards to memorize key concepts about quantum physics principles and phenomena.

📚 Glossary

Glossary

Quantum Physics: The branch of physics that describes the behavior of matter and energy at the atomic and subatomic scale, where classical physics fails to provide accurate predictions. It is based on the concept that energy, momentum, and other quantities are quantized.
Translation
Russian: Квантовая физика — раздел физики, описывающий поведение материи и энергии на атомном и субатомном уровне, где классическая физика не может дать точных предсказаний. Основана на концепции квантования энергии, импульса и других величин.
Kazakh: Кванттық физика — классикалық физика дәл болжамдар бере алмайтын атомдық және субатомдық деңгейде заттың және энергияның мінез-құлқын сипаттайтын физика саласы. Энергия, импульс және басқа шамалардың кванттанған тұжырымдамасына негізделген.
Wave-Particle Duality: The fundamental principle that all matter and energy exhibit both wave-like and particle-like properties, depending on the experimental setup used to observe them. This duality is most evident in the behavior of photons and electrons.
Translation
Russian: Корпускулярно-волновой дуализм — фундаментальный принцип, согласно которому вся материя и энергия проявляют как волновые, так и корпускулярные свойства, в зависимости от экспериментальной установки, используемой для их наблюдения. Этот дуализм наиболее очевиден в поведении фотонов и электронов.
Kazakh: Толқын-бөлшек қосарланғандығы — барлық зат пен энергия олларды бақылау үшін пайдаланылатын эксперименттік құрылысқа байланысты толқындық және бөлшектік қасиеттерді көрсететін іргелі принцип. Бұл қосарланғандық фотондар мен электрондардың мінез-құлқында ең айқын көрінеді.
Quantization: The concept that certain physical quantities, such as energy, angular momentum, and electric charge, can only exist in discrete values rather than any arbitrary value. This is a fundamental feature of quantum mechanics.
Translation
Russian: Квантование — концепция, согласно которой определенные физические величины, такие как энергия, угловой момент и электрический заряд, могут существовать только в дискретных значениях, а не в любых произвольных значениях. Это фундаментальная особенность квантовой механики.
Kazakh: Кванттау — энергия, бұрыштық импульс және электр заряды сияқты белгілі бір физикалық шамалардың кез келген ерікті мәнде емес, тек дискретті мәндерде ғана болуы мүмкін тұжырымдама. Бұл кванттық механиканың іргелі ерекшелігі.
Photoelectric Effect: The phenomenon where electrons are emitted from a material when light of sufficient frequency shines upon it. This effect provided crucial evidence for the particle nature of light and earned Einstein the Nobel Prize in Physics.
Translation
Russian: Фотоэлектрический эффект — явление, при котором электроны испускаются из материала при освещении его светом достаточной частоты. Этот эффект предоставил решающие доказательства корпускулярной природы света и принес Эйнштейну Нобелевскую премию по физике.
Kazakh: Фотоэлектрлік эффект — жеткілікті жиіліктегі жарық түскенде материалдан электрондардың шығарылуы құбылысы. Бұл эффект жарықтың бөлшектік табиғатына шешуші дәлелдемелер берді және Эйнштейнге физика бойынша Нобель сыйлығын әкелді.
Quantum Tunneling: The quantum mechanical phenomenon where a particle can pass through a potential energy barrier even when it lacks sufficient energy to go over the barrier classically. This effect is purely quantum and has no classical analog.
Translation
Russian: Квантовое туннелирование — квантово-механическое явление, при котором частица может пройти через потенциальный энергетический барьер, даже если у нее недостаточно энергии для преодоления барьера классическим способом. Этот эффект является чисто квантовым и не имеет классического аналога.
Kazakh: Кванттық туннельдеу — бөлшектің кедергіні классикалық түрде өтуге жеткіліксіз энергиясы болса да, потенциалдық энергия кедергісі арқылы өте алатын кванттық-механикалық құбылыс. Бұл эффект таза кванттық және классикалық аналогы жоқ.
Planck’s Constant (h): A fundamental physical constant that relates the energy of a photon to its frequency. Its value is approximately 6.626 × 10⁻³⁴ J·s. This constant is central to quantum mechanics and defines the scale at which quantum effects become important.
Translation
Russian: Постоянная Планка (h) — фундаментальная физическая константа, связывающая энергию фотона с его частотой. Ее значение составляет приблизительно 6,626 × 10⁻³⁴ Дж·с. Эта константа является центральной в квантовой механике и определяет масштаб, при котором квантовые эффекты становятся важными.
Kazakh: Планк тұрақтысы (h) — фотонның энергиясын оның жиілігімен байланыстыратын іргелі физикалық тұрақты. Оның мәні шамамен 6,626 × 10⁻³⁴ Дж·с. Бұл тұрақты кванттық механикада орталық және кванттық эффекттердің маңызды болатын масштабын анықтайды.
Uncertainty Principle: Heisenberg’s principle stating that certain pairs of physical properties (like position and momentum) cannot be measured simultaneously with perfect accuracy. The more precisely one property is measured, the less precisely the other can be known.
Translation
Russian: Принцип неопределенности — принцип Гейзенберга, утверждающий, что определенные пары физических свойств (такие как положение и импульс) нельзя измерить одновременно с идеальной точностью. Чем точнее измеряется одно свойство, тем менее точно можно определить другое.
Kazakh: Белгісіздік принципі — Гейзенбергтің белгілі бір физикалық қасиеттер жұбын (орын мен импульс сияқты) бір мезгілде мінсіз дәлдікпен өлшеуге болмайды деген принципі. Бір қасиет неғұрлым дәл өлшенсе, екіншісін соғұрлым аз дәл білуге болады.
Energy Levels: The discrete energy states that electrons can occupy in atoms. Electrons can only exist at specific energy levels and must absorb or emit specific amounts of energy (quanta) to transition between levels.
Translation
Russian: Энергетические уровни — дискретные энергетические состояния, которые могут занимать электроны в атомах. Электроны могут существовать только на определенных энергетических уровнях и должны поглощать или излучать определенные количества энергии (кванты) для перехода между уровнями.
Kazakh: Энергетикалық деңгейлер — атомдардағы электрондардың иемденуі мүмкін дискретті энергетикалық күйлер. Электрондар тек белгілі энергетикалық деңгейлерде ғана болуы мүмкін және деңгейлер арасында өту үшін белгілі мөлшердегі энергияны (кванттарды) жұтуы немесе шығаруы керек.
Photon: A quantum of electromagnetic radiation, representing the particle nature of light. Photons have no rest mass but carry energy proportional to their frequency (E = hf) and exhibit both wave and particle properties.
Translation
Russian: Фотон — квант электромагнитного излучения, представляющий корпускулярную природу света. Фотоны не имеют массы покоя, но несут энергию, пропорциональную их частоте (E = hf), и проявляют как волновые, так и корпускулярные свойства.
Kazakh: Фотон — жарықтың бөлшектік табиғатын көрсететін электромагниттік сәулеленудің кванты. Фотондардың тыныштық массасы жоқ, бірақ олардың жиілігіне пропорционал энергияны тасиды (E = hf) және толқындық пен бөлшектік қасиеттерді көрсетеді.

📖 Theory: Basic Principles of Quantum Physics

Theory: Understanding Quantum Mechanics and Its Revolutionary Concepts

Introduction to Quantum Physics

emerged in the early 20th century as scientists discovered that classical physics could not explain certain at the atomic and subatomic scale. This revolutionary theory fundamentally changed our understanding of .

Kazakh Translation

Кванттық физика XX ғасырдың басында ғалымдар классикалық физика атомдық және субатомдық масштабтағы белгілі бір құбылыстарды түсіндіре алмайтынын ашқан кезде пайда болды. Бұл революциялық теория біздің зат пен энергия туралы түсінігімізді іргелі түрде өзгертті.

Conceptual illustration showing the transition from classical to quantum physics

Historical Development

The development of quantum theory involved several key discoveries:

Kazakh Translation

Кванттық теорияның дамуы бірнеше маңызды ашулармен байланысты болды.

Year	Scientist	Discovery/Contribution	Significance
1900	Max Planck	Quantum hypothesis for blackbody radiation	Introduced energy quantization (E = hf)
1905	Albert Einstein	Photoelectric effect explanation	Established particle nature of light
1913	Niels Bohr	Atomic model with quantized orbits	Explained hydrogen spectrum
1924	Louis de Broglie	Matter waves hypothesis	Extended wave-particle duality to matter
1925-26	Heisenberg, Schrödinger	Quantum mechanics formulation	Complete mathematical framework

Wave-Particle Duality

One of the most remarkable aspects of quantum physics is wave-particle duality. Both light and matter exhibit properties of both waves and particles, depending on how they are observed.

Kazakh Translation

Кванттық физиканың ең таңғажайып аспектілерінің бірі — толқын-бөлшек қосарланғандығы. Жарық та, зат та олардың қалай бақыланатынына байланысты толқын мен бөлшектің қасиеттерін көрсетеді.

Double-slit experiment demonstrating wave-particle duality

Evidence for Wave-Particle Duality:

Wave Properties:

Interference patterns in double-slit experiments
Diffraction around obstacles
Wavelength and frequency relationships

Particle Properties:

Photoelectric effect
Compton scattering
Discrete energy transfer

Quantization of Energy

Energy quantization is a fundamental principle stating that energy can only exist in discrete packets called quanta.

Kazakh Translation

Энергияның кванттануы — энергия тек кванттар деп аталатын дискретті пакеттерде ғана болуы мүмкін деген іргелі принцип.

Planck’s Quantum Hypothesis

Max Planck proposed that electromagnetic radiation is emitted and absorbed in discrete energy packets:

E = hf

Where:

E = Energy of a quantum (Joules)
h = Planck’s constant (6.626 × 10⁻³⁴ J·s)
f = Frequency of radiation (Hz)

Kazakh Translation

E = кванттың энергиясы (Джоуль), h = Планк тұрақтысы (6.626 × 10⁻³⁴ Дж·с), f = сәулеленудің жиілігі (Гц).

The Photoelectric Effect

The photoelectric effect provided crucial evidence for the particle nature of light.

Kazakh Translation

Фотоэлектрлік эффект жарықтың бөлшектік табиғатына маңызды дәлелдемелер берді.

Photoelectric effect showing electron emission from metal surface

Key Observations:

Observation	Classical Prediction	Quantum Explanation
Threshold Frequency	No threshold expected	hf ≥ work function (φ)
Instantaneous Emission	Time delay expected	Immediate if f > f₀
Kinetic Energy vs Intensity	Should increase with intensity	Independent of intensity
Number of Electrons vs Intensity	Should be independent	Proportional to intensity

Einstein’s Photoelectric Equation:

hf = φ + ½mv²_max

Where φ is the work function (minimum energy needed to remove an electron)

Quantum Tunneling

is a purely quantum mechanical effect where particles can pass through that they classically should not be able to cross.

Kazakh Translation

Кванттық туннельдеу — бөлшектердің классикалық түрде өте алмайтын энергетикалық кедергілер арқылы өте алатын таза кванттық-механикалық эффект.

Quantum tunneling through a potential barrier

Applications of Quantum Tunneling:

Scanning Tunneling Microscope (STM): Uses tunneling current to image surfaces at atomic resolution
Nuclear Fusion: Enables fusion reactions in stars at lower energies than classically predicted
Electronics: Tunnel diodes and modern semiconductor devices
Radioactive Decay: Alpha particles tunnel out of atomic nuclei

Uncertainty Principle

Heisenberg’s uncertainty principle states that certain pairs of properties cannot be measured simultaneously with perfect precision.

Kazakh Translation

Гейзенбергтің белгісіздік принципі белгілі бір қасиеттер жұбын бір мезгілде мінсіз дәлдікпен өлшеуге болмайды деп тұжырымдайды.

Δx · Δp ≥ ℏ/2

Where ℏ = h/(2π) is the reduced Planck constant

Practice Questions

Question 1 (Easy):

Calculate the energy of a photon with frequency 5.0 × 10¹⁴ Hz. Use h = 6.626 × 10⁻³⁴ J·s.

Answer

Given: f = 5.0 × 10¹⁴ Hz, h = 6.626 × 10⁻³⁴ J·s
Using E = hf:
E = (6.626 × 10⁻³⁴) × (5.0 × 10¹⁴)
E = 3.313 × 10⁻¹⁹ J
Therefore, the photon energy is 3.31 × 10⁻¹⁹ J.

Question 2 (Medium):

Light of wavelength 400 nm strikes a metal surface with work function 2.5 eV. Calculate: (a) the photon energy in eV, (b) the maximum kinetic energy of emitted electrons.

Answer

Given: λ = 400 nm = 400 × 10⁻⁹ m, φ = 2.5 eV
Constants: h = 6.626 × 10⁻³⁴ J·s, c = 3.0 × 10⁸ m/s, 1 eV = 1.6 × 10⁻¹⁹ J

(a) Photon energy:
E = hc/λ = (6.626 × 10⁻³⁴ × 3.0 × 10⁸)/(400 × 10⁻⁹)
E = 4.97 × 10⁻¹⁹ J = 4.97 × 10⁻¹⁹ J ÷ (1.6 × 10⁻¹⁹ J/eV) = 3.11 eV

(b) Maximum kinetic energy:
KE_max = hf — φ = 3.11 eV — 2.5 eV = 0.61 eV
Therefore: (a) 3.11 eV, (b) 0.61 eV

Question 3 (Medium):

Explain why increasing the intensity of light below the threshold frequency in the photoelectric effect still produces no photoelectrons, even though more photons are present.

Answer

Quantum Explanation:
In the photoelectric effect, each electron interacts with a single photon in a one-to-one interaction. The energy required to remove an electron from the metal surface is the work function (φ).

Below threshold frequency:
— Each individual photon has energy E = hf < φ
— No single photon has enough energy to eject an electron
— Increasing intensity only increases the number of low-energy photons
— Electrons cannot «collect» energy from multiple photons simultaneously

Key Point: The photoelectric effect is a quantum phenomenon where energy transfer occurs in discrete packets (photons), not continuously as classical physics would predict. This is fundamentally different from classical wave theory, which would predict that increasing intensity (energy per unit area) should eventually provide enough energy regardless of frequency.

Question 4 (Critical Thinking):

The wave-particle duality seems to suggest that the nature of reality depends on how we observe it. Discuss the philosophical implications of quantum mechanics for our understanding of objective reality, and explain how the concept of complementarity resolves apparent contradictions in quantum behavior.

Answer

Philosophical Implications:

1. Observer-Dependent Reality:
— Quantum mechanics suggests that properties like wave/particle nature are not intrinsic but depend on experimental setup
— This challenges classical notions of objective reality existing independently of observation
— Measurement seems to «create» rather than just «reveal» properties

2. Complementarity Principle (Bohr):
— Wave and particle descriptions are complementary, not contradictory
— Both descriptions are necessary for complete understanding
— The experimental setup determines which aspect is observed
— Cannot observe both aspects simultaneously (similar to uncertainty principle)

3. Resolution of Contradictions:
— Apparent contradictions arise from applying classical thinking to quantum phenomena
— Quantum objects are neither waves nor particles in classical sense
— They are quantum entities that exhibit wave-like or particle-like behavior depending on interaction

4. Implications for Science:
— Questions the classical subject-object distinction
— Suggests fundamental limits to knowledge and predictability
— Emphasizes the role of measurement apparatus in defining reality
— Leads to concepts like quantum superposition and entanglement

Conclusion: Quantum mechanics doesn’t eliminate objective reality but redefines it, suggesting reality is more subtle and interconnected than classical physics assumed. The complementarity principle provides a framework for understanding these quantum phenomena without logical contradiction.

🧠 Memorization Exercises

Exercises on Memorizing Terms

Exercise 1: Quantum Formulas and Constants

Complete the fundamental quantum physics equations:

Planck’s equation: E = _____ × _____
Photoelectric equation: _____ = φ + KEmax
de Broglie wavelength: λ = _____ / _____
Uncertainty principle: Δx × Δp ≥ _____
Planck’s constant value: h = _____ J·s
Speed of light: c = _____ m/s

Answer

1. E = h × f (or E = hf)
2. hf = φ + KEmax
3. λ = h / p (where p is momentum)
4. Δx × Δp ≥ ℏ/2 (where ℏ = h/2π)
5. h = 6.626 × 10⁻³⁴ J·s
6. c = 3.0 × 10⁸ m/s

Exercise 2: Wave-Particle Duality Evidence

Match each phenomenon with the aspect of light it demonstrates:

Phenomena:

Double-slit interference
Photoelectric effect
Compton scattering
Diffraction around obstacles
Blackbody radiation
Young’s experiment

Aspects:

Wave nature
Particle nature

Answer

1-A: Double-slit interference → Wave nature
2-B: Photoelectric effect → Particle nature
3-B: Compton scattering → Particle nature
4-A: Diffraction around obstacles → Wave nature
5-B: Blackbody radiation → Particle nature (quantized energy)
6-A: Young’s experiment → Wave nature

Exercise 3: Quantum Pioneers and Discoveries

Match each scientist with their major contribution to quantum physics:

Scientist	Major Contribution
Max Planck	_______
Albert Einstein	_______
Niels Bohr	_______
Louis de Broglie	_______
Werner Heisenberg	_______

Answer

Max Planck: Quantum hypothesis and energy quantization (E = hf)
Albert Einstein: Photoelectric effect explanation (particle nature of light)
Niels Bohr: Atomic model with quantized energy levels
Louis de Broglie: Matter waves hypothesis (λ = h/p)
Werner Heisenberg: Uncertainty principle (Δx·Δp ≥ ℏ/2)

📺 Educational Video

Video Tutorial: Introduction to Quantum Physics

Additional Resources:

🔬 Problem Solving Examples

Worked Examples

Example 1: Photoelectric Effect Calculation

Problem: Ultraviolet light with wavelength 250 nm strikes a zinc surface (work function = 4.3 eV). Calculate: (a) photon energy, (b) maximum kinetic energy of emitted electrons, (c) stopping potential.

🎤 Audio Solution

Detailed Solution with Pronunciation

Given data (pronounced: DAY-ta):

λ = 250 nm = 250 × 10⁻⁹ m

Work function φ = 4.3 eV = 4.3 × 1.6 × 10⁻¹⁹ J = 6.88 × 10⁻¹⁹ J

Constants: h = 6.626 × 10⁻³⁴ J·s, c = 3.0 × 10⁸ m/s

Part (a): Photon energy calculation

Using E = hc/λ (pronounced: energy equals h-c over lambda)

E = (6.626 × 10⁻³⁴ × 3.0 × 10⁸) / (250 × 10⁻⁹)

E = 19.878 × 10⁻²⁶ / 250 × 10⁻⁹ = 7.95 × 10⁻¹⁹ J

Converting to eV: E = 7.95 × 10⁻¹⁹ / (1.6 × 10⁻¹⁹) = 4.97 eV

Part (b): Maximum kinetic energy

Using Einstein’s equation: KE_max = hf — φ

KE_max = 4.97 eV — 4.3 eV = 0.67 eV

In Joules: KE_max = 0.67 × 1.6 × 10⁻¹⁹ = 1.07 × 10⁻¹⁹ J

Part (c): Stopping potential

Stopping potential V_s = KE_max/e = 0.67 V

📝 Quick Solution

Brief Solution

Given: λ = 250 nm, φ = 4.3 eV

(a) Photon energy:
E = hc/λ = (6.626×10⁻³⁴ × 3×10⁸)/(250×10⁻⁹)
E = 7.95×10⁻¹⁹ J = 4.97 eV

(b) Maximum KE:
KE_max = hf — φ = 4.97 — 4.3 = 0.67 eV

(c) Stopping potential:
V_s = 0.67 V

Example 2: de Broglie Wavelength and Quantum Effects

Problem: Calculate the de Broglie wavelength for: (a) an electron moving at 2.0 × 10⁶ m/s, (b) a 0.1 kg baseball moving at 30 m/s. Comment on when quantum effects become significant.

🎤 Audio Solution

Detailed Solution with Pronunciation

de Broglie wavelength formula: λ = h/p = h/(mv)

Where h = 6.626 × 10⁻³⁴ J·s

Part (a): Electron wavelength

Given: m_e = 9.11 × 10⁻³¹ kg, v = 2.0 × 10⁶ m/s

Momentum: p = mv = (9.11 × 10⁻³¹) × (2.0 × 10⁶)

p = 1.822 × 10⁻²⁴ kg·m/s

λ = h/p = (6.626 × 10⁻³⁴) / (1.822 × 10⁻²⁴)

λ = 3.64 × 10⁻¹⁰ m = 0.364 nm

This is comparable to atomic dimensions!

Part (b): Baseball wavelength

Given: m = 0.1 kg, v = 30 m/s

Momentum: p = mv = 0.1 × 30 = 3.0 kg·m/s

λ = h/p = (6.626 × 10⁻³⁴) / 3.0

λ = 2.21 × 10⁻³⁴ m

This is incredibly small — far below any measurable scale!

When quantum effects matter:

Quantum effects become significant when λ ≈ size of system

For electrons: λ ~ atomic size → quantum effects important

For baseballs: λ << any macroscopic size → classical behavior

📝 Quick Solution

Brief Solution

Formula: λ = h/(mv)

(a) Electron:
m = 9.11×10⁻³¹ kg, v = 2.0×10⁶ m/s
λ = (6.626×10⁻³⁴)/[(9.11×10⁻³¹)(2.0×10⁶)] λ = 3.64×10⁻¹⁰ m = 0.364 nm

(b) Baseball:
m = 0.1 kg, v = 30 m/s
λ = (6.626×10⁻³⁴)/(0.1×30)
λ = 2.21×10⁻³⁴ m

Significance: Quantum effects matter when λ ≈ object size

🔬 Investigation Task

Interactive Simulation

Use this PhET simulation to explore quantum phenomena and wave-particle duality:

Investigation Questions:

How does the double-slit pattern change when you switch from waves to particles (photons/electrons)?
What happens to the interference pattern when you try to detect which slit the particle goes through?
How does the intensity affect the pattern formation in both wave and particle modes?
Observe the photoelectric effect simulation — how does changing frequency vs. intensity affect electron emission?

Brief Answers

1. Both waves and particles create interference patterns, demonstrating wave-particle duality — particles behave like waves when not observed
2. Detection destroys the interference pattern — the «which path» information eliminates wave-like behavior (measurement collapses the wave function)
3. Higher intensity increases the number of particles but doesn’t change the pattern shape — individual particles still follow probabilistic wave behavior
4. Frequency determines whether electrons are emitted and their maximum energy; intensity only affects the number of emitted electrons, not their individual energies

👥 Group/Pair Activity

Collaborative Learning Activity

Work with your partner or group to complete this quantum physics exploration challenge:

Discussion Points:

How did quantum physics revolutionize our understanding of the nature of reality?
What practical technologies rely on quantum principles, and how do they work?
How do the philosophical implications of quantum mechanics challenge classical intuition?
What role does the observer play in quantum measurements, and why is this controversial?

Group Challenge Activities:

Design experiments to demonstrate wave-particle duality using everyday analogies
Calculate quantum effects for various particles and determine when classical physics breaks down
Investigate applications of quantum tunneling in modern technology
Explore the historical debates between Einstein and Bohr about quantum interpretations

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