OCR A Level Physics A
OCR A Level Physics A Module 4: Electrons, Waves and Photons Exam Questions
Free OCR A Level Physics A exam questions for Module 4: Electrons, Waves and Photons, with a mark scheme for every pack. Covers charge and current, resistance and resistivity, power, Kirchhoff's laws, potential dividers, internal resistance, waves, interference and quantum physics.
Module 4: Electrons, Waves and Photons exam questions
5 question packs of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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A-Level Physics Flashcards for 2027 Onwards
Every answer is written in mark scheme wording, so you learn exactly what examiners give marks for. Then test yourself with the questions on this page.
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About OCR A Level Physics A Module 4: Electrons, Waves and Photons
Module 4 of OCR A Level Physics A, Electrons, Waves and Photons, covers electricity, waves and the beginnings of quantum physics. It includes charge, current and mean drift velocity, resistance, resistivity and I-V characteristics, power, Kirchhoff's laws, potential dividers, EMF and internal resistance, progressive and stationary waves, polarisation, interference and diffraction, and photons with the photoelectric effect and wave-particle duality. It feeds into capacitors and electric fields in Module 6. Examiners test circuit analysis, resistivity practicals, Young's double slit and diffraction gratings, stationary wave harmonics and photoelectric calculations using the Einstein equation.
What you need to know
- 4.1 Current I = Delta Q / Delta t, conservation of charge and Kirchhoff's first law, mean drift velocity I = Anev, and conductors, semiconductors and insulators.
- 4.2 Potential difference and EMF, resistance and Ohm's law, I-V characteristics of resistors, filament lamps and diodes, resistivity R = rho L / A, thermistors, LDRs and power P = VI = I^2 R.
- 4.3 Kirchhoff's second law, series and parallel circuits, internal resistance E = I(R + r), and potential divider circuits with sensors.
- 4.4 Wave properties, the wave equation v = f lambda, intensity, polarisation, reflection, refraction, diffraction, superposition, Young's double slit lambda = ax / D, diffraction gratings and stationary waves with nodes and antinodes.
- 4.5 Photons E = hf, the electronvolt, LEDs to determine h, the photoelectric effect with hf = phi + KEmax, and electron diffraction with the de Broglie wavelength lambda = h / p.
Common mistakes in Module 4: Electrons, Waves and Photons
- Saying EMF and terminal potential difference are always equal. Terminal p.d. is less than EMF when current flows because of lost volts across internal resistance (Ir).
- Stating that resistivity depends on the length of a wire. Resistivity is a property of the material; resistance depends on length and area.
- Assuming the distance between adjacent nodes is a wavelength. Adjacent nodes are half a wavelength apart.
- Saying photoelectrons are emitted after a delay at low intensity. Emission is instantaneous above the threshold frequency because each photon interacts with one electron.
- Treating a thermistor's resistance as increasing with temperature. An NTC thermistor's resistance decreases as temperature rises.
Try three Module 4: Electrons, Waves and Photons exam-style questions
1. A cell of EMF 6.0 V and internal resistance 0.50 ohm is connected to a 5.5 ohm resistor. Calculate the current and the terminal potential difference. (3 marks)
Show the mark scheme answer
I = E / (R + r) = 6.0 / 6.0 = 1.0 A; terminal p.d. = IR = 1.0 x 5.5 = 5.5 V; lost volts = 0.5 V.
2. Light of wavelength 600 nm passes through a grating with 300 lines per mm. Calculate the angle of the second order maximum. (3 marks)
Show the mark scheme answer
d = 1 / 300 000 = 3.33 x 10^-6 m; sin(theta) = n lambda / d = 2 x 600 x 10^-9 / 3.33 x 10^-6 = 0.36; theta = 21 degrees.
3. Explain how the photoelectric effect provides evidence for the particle nature of light. (3 marks)
Show the mark scheme answer
No emission below a threshold frequency, however intense the light; maximum kinetic energy depends on frequency not intensity; explained by one photon transferring all its energy to one electron, which wave theory cannot explain.
Module 4: Electrons, Waves and Photons FAQs
What does OCR A Level Physics A Module 4: Electrons, Waves and Photons cover?
Charge and current, energy, power and resistance, electrical circuits, waves and quantum physics.
Which papers is Module 4 examined in?
It is assessed in Paper 2 (Exploring physics) and Paper 3 (Unified physics); it is also assessed at AS.
Which practicals come up in Module 4?
Determining resistivity of a wire, investigating EMF and internal resistance, finding the wavelength of light with a grating, and determining the Planck constant using LEDs.
