IB Physics Flashcards: Nuclear and Quantum Physics
IB Physics — Nuclear and Quantum Physics Flashcard Deck
Flashcards with spaced repetition. Press Space to flip, then rate your recall (1—4).
Key Concepts
Mass Defect and Binding Energy: The mass of a nucleus is always less than the sum of the masses of its individual nucleons. This “missing mass” is the mass defect (Δm), and it corresponds to the binding energy via E = Δmc². A higher binding energy per nucleon means a more stable nucleus — iron-56 has the highest binding energy per nucleon (~8.8 MeV/nucleon). This is why fission of heavy nuclei (uranium) and fusion of light nuclei (hydrogen) both release energy — they move toward iron-56 on the binding energy curve. The binding energy curve explains why stars shine (fusion) and why nuclear power plants work (fission).
Radioactive Decay Law states that N = N₀e^(−λt), where N₀ is the initial number of undecayed nuclei, λ is the decay constant, and t₁/₂ = ln2/λ is the half-life. Activity A also follows A = A₀e^(−λt). The decay constant λ represents the probability that a single nucleus will decay per unit time. The half-life is the time for half the nuclei to decay. This law is fundamentally probabilistic — you can predict how many nuclei remain on average, but you cannot predict which specific nucleus will decay next. This is a key insight of quantum physics.
Photoelectric Effect demonstrated that light behaves as particles (photons). A photon of energy hf ejects an electron only if hf exceeds the work function φ of the metal. The maximum kinetic energy of the emitted electron is KEmax = hf − φ. Increasing light intensity increases the number of electrons (more photons), not their energy. This effect cannot be explained by wave theory — it requires the particle model of light. The existence of a threshold frequency is the key evidence for the particle model.
de Broglie Wavelength links wave and particle nature: λ = h/p, where h is Planck’s constant and p is momentum. This applies to all matter, not just light. Electrons can produce diffraction patterns because their de Broglie wavelength is comparable to atomic spacings (~10⁻¹⁰ m). This was confirmed by electron diffraction experiments and is the basis for electron microscopy.
Intuition
Think of binding energy as the “glue cost” needed to pull a nucleus apart. Just as you must do work to separate two magnets, you must supply energy to overcome the strong nuclear force holding nucleons together. The mass defect is the mass equivalent of that energy — mass itself is a form of stored energy, as Einstein showed. For the photoelectric effect, imagine photons as discrete energy packets: one photon either has enough energy to kick out an electron, or it doesn’t — no amount of weak photons will do the job. The de Broglie wavelength is nature’s way of saying that everything has both wave and particle properties — it’s just that for everyday objects, the wavelength is so small we never notice.
Why it matters: Nuclear physics explains how stars produce energy, how nuclear power works, and how medical imaging and radiation therapy function. Quantum physics is the foundation of modern technology — semiconductors, lasers, and MRI all rely on quantum principles.
Common Pitfalls
- Confusing the decay constant λ with half-life: they are inversely related. A larger λ means faster decay (shorter half-life), not slower. The relationship is t₁/₂ = ln2/λ.
- Thinking that increasing light intensity in the photoelectric effect increases electron KE. Intensity increases the number of photons (and thus electrons), but each electron’s KE depends only on the photon frequency. Only increasing frequency increases electron KE.
- Forgetting that alpha, beta, and gamma radiation have different ionising powers and penetrating abilities. Alpha is most ionising but least penetrating (stopped by paper); gamma is least ionising but most penetrating (requires thick lead). This has practical implications for shielding and safety.
- Assuming the binding energy curve is flat. It has a clear peak at iron-56, which explains why both fission and fusion release energy for elements on either side of iron.
Cross-References
- Kinematics: Kinematics describes particle motion, and quantum physics reveals that particles also behave as waves.
- Mechanics: Mechanics covers energy conservation, which underpins nuclear energy calculations and binding energy.
- Thermal Physics: Thermal physics connects to nuclear physics through temperature as a measure of average kinetic energy and through nuclear reactions in stars.
- Waves: Wave-particle duality connects wave phenomena (interference, diffraction) with particle properties (photoelectric effect, de Broglie wavelength).
Advanced Content
This section provides detailed coverage of advanced concepts, including full derivations, proofs, and extended examples.
Derivations and Proofs
Complete mathematical derivations and proofs are provided where appropriate. Each step is explained to ensure understanding of the underlying reasoning.
Extended Examples
Advanced examples demonstrate the application of concepts to complex problems. These examples go beyond standard exam questions to develop deeper understanding.
Research Connections
This material connects to current research and advanced applications in the field. Understanding these connections provides context for the study material.
Prerequisites
Ensure you have mastered the prerequisite material before attempting this advanced content.
Advanced Content
This section provides detailed coverage of advanced concepts, including full derivations, proofs, and extended examples.
Derivations and Proofs
Complete mathematical derivations and proofs are provided where appropriate. Each step is explained to ensure understanding of the underlying reasoning.
Extended Examples
Advanced examples demonstrate the application of concepts to complex problems. These examples go beyond standard exam questions to develop deeper understanding.
Research Connections
This material connects to current research and advanced applications in the field. Understanding these connections provides context for the study material.
Prerequisites
Ensure you have mastered the prerequisite material before attempting this advanced content.
Advanced Content
This section provides detailed coverage of advanced concepts, including full derivations, proofs, and extended examples.
Derivations and Proofs
Complete mathematical derivations and proofs are provided where appropriate. Each step is explained to ensure understanding of the underlying reasoning.
Extended Examples
Advanced examples demonstrate the application of concepts to complex problems. These examples go beyond standard exam questions to develop deeper understanding.
Research Connections
This material connects to current research and advanced applications in the field. Understanding these connections provides context for the study material.
Prerequisites
Ensure you have mastered the prerequisite material before attempting this advanced content.
Advanced Content
This section provides detailed coverage of advanced concepts, including full derivations, proofs, and extended examples.
Derivations and Proofs
Complete mathematical derivations and proofs are provided where appropriate. Each step is explained to ensure understanding of the underlying reasoning.
Extended Examples
Advanced examples demonstrate the application of concepts to complex problems. These examples go beyond standard exam questions to develop deeper understanding.
Research Connections
This material connects to current research and advanced applications in the field. Understanding these connections provides context for the study material.
Prerequisites
Ensure you have mastered the prerequisite material before attempting this advanced content.
Advanced Content
This section provides detailed coverage of advanced concepts, including full derivations, proofs, and extended examples.
Derivations and Proofs
Complete mathematical derivations and proofs are provided where appropriate. Each step is explained to ensure understanding of the underlying reasoning.
Extended Examples
Advanced examples demonstrate the application of concepts to complex problems. These examples go beyond standard exam questions to develop deeper understanding.
Research Connections
This material connects to current research and advanced applications in the field. Understanding these connections provides context for the study material.
Prerequisites
Ensure you have mastered the prerequisite material before attempting this advanced content.
Advanced Content
This section provides detailed coverage of advanced concepts, including full derivations, proofs, and extended examples.
Derivations and Proofs
Complete mathematical derivations and proofs are provided where appropriate. Each step is explained to ensure understanding of the underlying reasoning.
Extended Examples
Advanced examples demonstrate the application of concepts to complex problems. These examples go beyond standard exam questions to develop deeper understanding.
Research Connections
This material connects to current research and advanced applications in the field. Understanding these connections provides context for the study material.
Prerequisites
Ensure you have mastered the prerequisite material before attempting this advanced content.
Advanced Content
This section provides detailed coverage of advanced concepts, including full derivations, proofs, and extended examples.
Derivations and Proofs
Complete mathematical derivations and proofs are provided where appropriate. Each step is explained to ensure understanding of the underlying reasoning.
Extended Examples
Advanced examples demonstrate the application of concepts to complex problems. These examples go beyond standard exam questions to develop deeper understanding.
Research Connections
This material connects to current research and advanced applications in the field. Understanding these connections provides context for the study material.
Prerequisites
Ensure you have mastered the prerequisite material before attempting this advanced content.
Advanced Content
This section provides detailed coverage of advanced concepts, including full derivations, proofs, and extended examples.
Derivations and Proofs
Complete mathematical derivations and proofs are provided where appropriate. Each step is explained to ensure understanding of the underlying reasoning.
Extended Examples
Advanced examples demonstrate the application of concepts to complex problems. These examples go beyond standard exam questions to develop deeper understanding.
Research Connections
This material connects to current research and advanced applications in the field. Understanding these connections provides context for the study material.
Prerequisites
Ensure you have mastered the prerequisite material before attempting this advanced content.
Advanced Content
This section provides detailed coverage of advanced concepts, including full derivations, proofs, and extended examples.
Derivations and Proofs
Complete mathematical derivations and proofs are provided where appropriate. Each step is explained to ensure understanding of the underlying reasoning.
Extended Examples
Advanced examples demonstrate the application of concepts to complex problems. These examples go beyond standard exam questions to develop deeper understanding.
Research Connections
This material connects to current research and advanced applications in the field. Understanding these connections provides context for the study material.
Prerequisites
Ensure you have mastered the prerequisite material before attempting this advanced content.