Numbers
CCEA A-Level Physics 1210
Physical Quantities, Scalars and Vectors
Moments and Equilibrium
Linear Motion and Dynamics
Newton's Laws of Motion
Linear Momentum and Impulse
Work, Energy and Power
Current, Charge and Potential Difference
Resistance and Resistivity
Topic overviewResistance and Ohm's lawOhmic and non-ohmic behaviourResistors in series and in parallelInvestigating current, voltage and resistance in series and parallel circuitsElectrical power and energy in resistive circuitsResistivity and the equation R = ρl/AMeasuring the resistivity of a metalCurrent–voltage characteristics of a conductor, a lamp and a diodeResistance, temperature and superconductivity
Internal Resistance and Potential Dividers
Topic overviewInternal resistance and terminal potential differenceConsequences of internal resistance for external circuitsMeasuring electromotive force and internal resistanceThe potential divider and variable outputPotential dividers in lighting and heating control circuitsLoaded potential dividers and output voltage calculations
Waves
Refraction
Lenses
Superposition, Interference and Diffraction
Topic overviewSuperposition of wavesStanding waves, nodes and antinodesStanding waves on stretched stringsStanding waves in a pipe closed at one endMeasuring the speed of sound with a resonance tubeConditions for observable interferencePath difference and phase differenceYoung's double slitDiffraction at a single slitThe diffraction grating
Quantum Physics
Wave-Particle Duality
Astronomy
Practical Skills and Data Analysis
Topic overviewChoosing and using measuring instrumentsPrecision, accuracy and recording measurementsUsing the cathode ray oscilloscope to measure voltage and frequencyTables, graphs and presenting resultsLinearising a relationship and using the gradientAbsolute and percentage uncertaintyCombining uncertainties and uncertainty on a graphRandom and systematic error, reliability and refining an experiment
Deformation of Solids
Thermal Physics
Topic overviewBoyle's law, Charles's law and the pressure lawThe ideal gas equation pV = nRTThe Avogadro constant, the mole and pV = NkTInternal energy and the distribution of molecular energyThe kinetic theory equation pV = ⅓Nm⟨c²⟩Average molecular kinetic energy and temperatureAbsolute zero and the kelvin scaleSpecific heat capacity and the electrical method
Uniform Circular Motion
Simple Harmonic Motion
Topic overviewDefining simple harmonic motion and a = −ω²xDisplacement, velocity and acceleration: x = A cos ωtThe simple pendulum and T = 2π√(l/g)The loaded spiral spring and T = 2π√(m/k)SHM graphs and finding velocity from a gradientFree vibrations, forced vibrations and resonanceDamping: light, critical and over-damping
The Nucleus and Radioactive Decay
Topic overviewAlpha-particle scattering and the nuclear atomNuclear radius and nucleon numberThe density of nuclear matterAlpha, beta and gamma radiation: nature, penetration and rangeNuclear equations and changes in nucleon and proton numberThe random and exponential nature of radioactive decayActivity, the decay constant and A = −λNExponential decay calculations with A = A₀e^(−λt)Half-life and measuring it
Nuclear Energy, Fission and Fusion
Gravitational Fields
Electric Fields
Capacitors
Magnetic Fields
Charged Particles and Accelerators
Refraction
Snell's law
- 3 things to know
- Unit AS 2
Overview
Recall questions on the statement of Snell's law and its air-to-medium form, the definition of the angle of incidence and why angles are measured from the normal, worked calculations across air-to-glass and water-to-glass boundaries, the law written in terms of speeds and of wavelengths, and the graph of sin i against sin r.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Numbers
A ray inside glass of refractive index 1.50 meets the surface at 20° to the normal and emerges into air. Calculate the angle in air.
Key term
State Snell's law in the simpler form used when light travels from air into a material.
Questions from this subtopic
Each one with the model answer underneath.
- 1
State Snell's law for a ray crossing a boundary between two media, defining each symbol.
Model answer
n₁ sin θ₁ = n₂ sin θ₂, where n₁ and n₂ are the refractive indices of the first and second media and θ₁ and θ₂ are the angles between the ray and the normal in each medium.
- 2
State Snell's law in the simpler form used when light travels from air into a material.
Model answer
n = sin i / sin r, where n is the refractive index of the material, i is the angle of incidence in air and r is the angle of refraction in the material, both measured from the normal.
- 3
Define the angle of incidence.
Model answer
The angle of incidence is the angle between the incident ray and the normal to the surface at the point where the ray strikes it.
- 4
Why are the angles in Snell's law measured from the normal rather than from the surface?
Model answer
The normal gives a single well-defined reference line at any point on a surface, including a curved one, and it keeps the law in the same form for every shape of boundary.
- 5
Light strikes a glass block of refractive index 1.50 at an angle of incidence of 30°. Calculate the angle of refraction.
Model answer
sin r = sin 30° / 1.50 = 0.500/1.50 = 0.333, so r = 19.5°, and 1.50 × sin 19.5° = 0.500 = sin 30° as given.
- 6
A ray inside glass of refractive index 1.50 meets the surface at 20° to the normal and emerges into air. Calculate the angle in air.
Model answer
sin θₐᵢᵣ = 1.50 × sin 20° = 1.50 × 0.342 = 0.513, so θₐᵢᵣ = 30.9°, and sin 30.9° ÷ 1.50 returns sin 20° as given.
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