Waves and Electricity

Worked examples (9)

• 1Classifying transverse and longitudinal waves (2 marks)
• 2Using the wave equation v = fλ (2 marks)
• 3Linking period and frequency (2 marks)
• 4Rearranging the wave equation for wavelength (3 marks)
• 5Reading period and wavelength from two graphs (4 marks)
• 6Phase difference between two points on a wave (3 marks)
• 7Intensity and the inverse-square law for a point source (5 marks)
• 8Core Practical 4 — speed of sound from phase comparison (6 marks)
• 9Show that — distance to a cliff from an echo (6 marks)

Model answers (10)

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• ✓Model answer — Adapted from Edexcel IAL Physics Unit 2 (Core Practical 4)
• ✓Model answer — Adapted from Edexcel IAL Physics Unit 2
• ✓Model answer — Adapted from Edexcel IAL Physics Unit 2

Worked examples (9)

• 1Resultant displacement by superposition (2 marks)
• 2Path difference for constructive interference (2 marks)
• 3Wavelength from node spacing (2 marks)
• 4Speed of a wave on a string from tension and mass per unit length (3 marks)
• 5Fundamental frequency of a vibrating string (4 marks)
• 6Identifying a harmonic from the number of antinodes (4 marks)
• 7Show that the fundamental frequency formula gives a stated value (5 marks)
• 8Determining mass per unit length from a CP5 graph (6 marks)
• 9Two-source interference: explaining a bright fringe (6 marks)

Model answers (10)

• ✓Model answer 1
• ✓Model answer 2
• ✓Model answer 3
• ✓Model answer 4
• ✓Model answer 5
• ✓Model answer 6
• ✓Model answer 7
• ✓Model answer — Adapted from Edexcel IAL Physics Unit 2 (Core Practical 5)
• ✓Model answer — Adapted from Edexcel IAL Physics Unit 2
• ✓Model answer — Adapted from Edexcel IAL Physics Unit 2

Worked examples (9)

• 1Refractive index from the speed of light (2 marks)
• 2Snell's law: angle of refraction entering glass (3 marks)
• 3Critical angle of a glass–air boundary (2 marks)
• 4Refraction at a glass–water boundary (3 marks)
• 5Determining the refractive index of a glass block (4 marks)
• 6Total internal reflection in a 45° prism (3 marks)
• 7Maximum angle for guiding in an optical fibre (5 marks)
• 8Crossed polarising filters (4 marks)
• 9Why only light, not sound, can be polarised (3 marks)

Model answers (10)

• ✓Model answer 1
• ✓Model answer 2
• ✓Model answer 3
• ✓Model answer 4
• ✓Model answer 5
• ✓Model answer 6
• ✓Model answer 7
• ✓Model answer — Adapted from Edexcel IAL Physics Unit 2
• ✓Model answer — Adapted from Edexcel IAL Physics Unit 2
• ✓Model answer — Adapted from Edexcel IAL Physics Unit 2

Worked examples (9)

• 1Energy of a single photon (2 marks)
• 2Slit spacing from lines per millimetre (2 marks)
• 3de Broglie wavelength of a moving electron (3 marks)
• 4Diffraction angle of a grating order (3 marks)
• 5Wavelength of a photon from its energy (3 marks)
• 6Converting a photon energy to electronvolts (4 marks)
• 7Finding laser wavelength from a higher order (5 marks)
• 8de Broglie wavelength after acceleration (6 marks)
• 9Maximum number of orders from a grating (6 marks)

Model answers (10)

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Worked examples (9)

• 1Energy of a single photon (2 marks)
• 2Converting an energy from electronvolts to joules (2 marks)
• 3Threshold frequency from the work function (3 marks)
• 4Maximum kinetic energy from Einstein's equation (3 marks)
• 5Stopping potential from maximum kinetic energy (3 marks)
• 6Wavelength of an emitted spectral line (4 marks)
• 7Why the wave model cannot explain a threshold frequency (6 marks)
• 8Determining the Planck constant from a KEmax–f graph (6 marks)
• 9Absorption line and the emitted photon's frequency (6 marks)

Model answers (10)

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Worked examples (9)

• 1Charge delivered by a steady current (2 marks)
• 2Resistance from a voltmeter and ammeter reading (2 marks)
• 3Power dissipated in a lamp (3 marks)
• 4Resistance of a filament lamp at two operating points (4 marks)
• 5Resistance of a series–parallel network (4 marks)
• 6Power dissipation using I²R (3 marks)
• 7Current division in a parallel circuit (5 marks)
• 8Potential difference division and power in a series circuit (6 marks)
• 9Deriving the parallel-resistance formula from Kirchhoff's laws (6 marks)

Model answers (10)

• ✓Model answer 1
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• ✓Model answer 9
• ✓Model answer — Adapted from Edexcel IAL Physics Unit 2

Worked examples (9)

• 1e.m.f. from energy and charge (2 marks)
• 2Terminal p.d. and lost volts (3 marks)
• 3Combining identical cells in series (3 marks)
• 4Finding internal resistance from one measurement (4 marks)
• 5Using ε = I(R + r) to find the current (3 marks)
• 6Determining ε and r from a V–I graph (5 marks)
• 7Short-circuit current of a cell (4 marks)
• 8Internal resistance from two load settings (6 marks)
• 9Power delivered to the load and lost in the cell (6 marks)

Model answers (10)

• ✓Model answer 1
• ✓Model answer 2
• ✓Model answer 3
• ✓Model answer 4
• ✓Model answer 5
• ✓Model answer — Adapted from Edexcel IAL Physics Unit 2 (CP8)
• ✓Model answer — Adapted from Edexcel IAL Physics Unit 2 (CP8)
• ✓Model answer 8
• ✓Model answer 9
• ✓Model answer — Adapted from Edexcel IAL Physics Unit 2 (CP8)