Edexcel A Level Physics
Edexcel A Level Physics Topic 5: Waves and the Particle Nature of Light Exam Questions
Free Edexcel A Level Physics exam questions for Topic 5: Waves and the Particle Nature of Light, with a mark scheme for every pack. Covers progressive and stationary waves, refraction, lenses, polarisation, interference, diffraction gratings, the photoelectric effect, electron diffraction and energy levels.
Topic 5: Waves and the Particle Nature of Light exam questions
4 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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About Edexcel A Level Physics Topic 5: Waves and the Particle Nature of Light
Topic 5: Waves and the Particle Nature of Light is one of the largest topics in Edexcel A Level Physics. It covers wave properties and stationary waves, reflection, refraction and lenses, interference and diffraction, and the particle nature of light. You use v = fλ, v = √(T/μ), refractive index, lens equations, nλ = d sin θ, the photoelectric equation and the de Broglie wavelength. Core practicals include measuring the speed of sound with an oscilloscope, investigating waves on a string and using a diffraction grating. It is assessed in Paper 2: Advanced Physics II. Examiners like wave-particle duality explanations.
What you need to know
- Wave properties v = fλ; transverse and longitudinal waves; phase and path difference; intensity I = P/A. Pulse-echo techniques use reflected waves to measure distance.
- Stationary waves Formed by superposition of two waves travelling in opposite directions. On a string, v = √(T/μ) and adjacent nodes are λ/2 apart.
- Refraction and lenses n = c/v and n1 sin θ1 = n2 sin θ2; total internal reflection when sin C = 1/n. Lens power P = 1/f, 1/u + 1/v = 1/f and magnification m = v/u.
- Polarisation Only transverse waves can be plane polarised. Polarising filters are used in stress analysis and to reduce glare.
- Interference and diffraction Coherent sources give stable interference patterns. Diffraction grating: nλ = d sin θ. Electron diffraction is evidence that electrons behave as waves, with λ = h/p.
- Particle nature of light Photon energy E = hf. Photoelectric equation hf = φ + ½mvmax^2. Energy levels in atoms explain line spectra: hf = E1 - E2. The electronvolt converts energies.
Common mistakes in Topic 5: Waves and the Particle Nature of Light
- Saying brighter light increases the kinetic energy of photoelectrons. It increases the number emitted per second.
- Using lines per mm directly as d in nλ = d sin θ.
- Saying nodes are one wavelength apart. They are half a wavelength apart.
- Using m = u/v instead of v/u for magnification.
- Calling the wave model's failure 'light can't be a wave'. Say the wave model predicts that any frequency would eventually cause emission and that intensity would affect kinetic energy, which is not observed.
Try three Topic 5: Waves and the Particle Nature of Light exam-style questions
1. A string under tension 40 N has mass per unit length 4.0 × 10^-3 kg m^-1 and length 0.80 m. Calculate the frequency of its fundamental mode. (3 marks)
Show the mark scheme answer
v = √(T/μ) = √(40/4.0 × 10^-3) = 100 m s^-1; λ = 2 × 0.80 = 1.6 m; f = v/λ = 62.5 Hz.
2. An object is placed 0.15 m from a converging lens of focal length 0.10 m. Calculate the image distance and the magnification. (3 marks)
Show the mark scheme answer
1/v = 1/0.10 - 1/0.15 = 3.33 m^-1; v = 0.30 m; m = v/u = 0.30/0.15 = 2.0.
3. Explain how the photoelectric effect provides evidence for the particle nature of light. (4 marks)
Show the mark scheme answer
Electrons are only emitted above a threshold frequency regardless of intensity; one photon gives all its energy hf to one electron; if hf is less than the work function no electron is released; emission is instantaneous, whereas a wave model predicts a time delay at low intensity and emission at any frequency.
Topic 5: Waves and the Particle Nature of Light FAQs
What does Edexcel A Level Physics Topic 5 cover?
It covers wave properties, stationary waves, refraction, lenses, polarisation, interference and diffraction, the photoelectric effect, electron diffraction and atomic energy levels.
Which paper is Topic 5 examined in?
It is assessed in Paper 2: Advanced Physics II, and like every topic it can also appear in Paper 3: General and Practical Principles in Physics.
Which core practicals are in Topic 5?
Determining the speed of sound in air using an oscilloscope, signal generator, speaker and microphone; investigating waves on a string; and determining the wavelength of light with a diffraction grating.
