Waves and Particle Nature of Light | Edexcel A-Level Physics (9PH0)

Waves and Particle Nature of Light

288 questions
29 subtopics
Paper 2: Advanced Physics II
Paper 2 and Paper 3

The largest topic on Paper 2 and the one that carries the course from classical waves to quantum behaviour: wave properties and the wave equation, superposition, stationary waves, refraction and total internal reflection, lenses, polarisation and diffraction, and then de Broglie, photons, line spectra and the photoelectric effect..

It covers describing a progressive wave, the wave equation and its use, longitudinal and transverse waves, displacement-distance and displacement-time graphs, measuring the speed of sound with an oscilloscope, wavefronts, superposition and phase, coherence, path difference and phase difference, interference in practice, stationary waves, nodes and antinodes, harmonics on a stretched string, investigating a vibrating string, and air columns, intensity, the inverse square law and refractive index, refraction, wave speed and the critical angle, total internal reflection and measuring refractive index, lenses, ray diagrams and the images they form, lens power and the thin lens equation, lens calculations and magnification, reflection, transmission and the pulse-echo principle, pulse-echo calculations, resolution and ultrasound, polarisation and diffraction, single-slit patterns and the diffraction grating equation, grating spectra and measuring wavelength, electron diffraction and the de Broglie equation, de Broglie calculations and wave-particle duality, photons and photon energy, models of light and the electronvolt, line spectra and atomic energy levels, the photoelectric effect and Einstein's equation and evidence for the photon model and photoelectric calculations.

Sample questions from Waves and Particle Nature of Light

Answer each one closed book first, then open the answer.

Describing a progressive wave

What is meant by the wavelength of a wave?

Show the answer
The wavelength is the shortest distance between two points on the wave that are oscillating in phase, such as one crest and the next.
Displacement-distance and displacement-time graphs

How is a node identified on a displacement graph of a stationary wave?

Show the answer
A node is a position where the displacement is permanently zero, so every trace of the wave crosses the axis at that same point.
Interference in practice

Why does walking along a line in front of two loudspeakers emitting the same note produce alternating loud and quiet regions?

Show the answer
The two distances to the listener change at different rates, so the path difference cycles through whole and half-integer numbers of wavelengths, giving alternate constructive and destructive interference.
Investigating a vibrating string, and air columns

How can the uncertainty in locating the resonant frequency be reduced?

Show the answer
Approach the resonance from above and below, note the range of frequencies over which the loop amplitude is largest, and take the mid-point of that range as the resonant frequency.
Lenses, ray diagrams and the images they form

How is a ray arriving parallel to the axis of a diverging lens refracted?

Show the answer
It emerges travelling as though it had come from the principal focus on the same side of the lens as the object.
Reflection, transmission and the pulse-echo principle

What two quantities must a pulse-echo system know or measure in order to locate an object?

Show the answer
It needs the speed of the wave in the medium and the time taken for the pulse to travel out and return.
Grating spectra and measuring wavelength

How can the wavelength of light from a laser be found using a diffraction grating?

Show the answer
Direct the beam normally at a grating of known slit spacing, measure the perpendicular distance to a screen and the distance of a given order from the central maximum, find θ from the tangent of these distances, then calculate λ from λ = d sinθ / n.
Photons and photon energy

What is the energy of that 5.00 × 10⁻⁷ m photon in electronvolts?

Show the answer
Dividing by 1.60 × 10⁻¹⁹ gives 2.49 eV.

The 29 subtopics

One subtopic is one session. Work down the list.

Subtopic	What it covers	Questions
Describing a progressive wave	Recall questions on amplitude, wavelength, frequency and period, why amplitude is not the peak-to-peak value, and how energy carried depends on amplitude.	10
The wave equation and its use	Recall questions on v = fλ and where it comes from, and on what happens to speed, frequency and wavelength when a wave crosses into a new medium.	11
Longitudinal and transverse waves	Recall questions on the difference between the two, examples of each, compressions and rarefactions, and why sound cannot travel through a vacuum.	10
Displacement-distance and displacement-time graphs	Recall questions on what each axis shows, telling the two graphs apart, how a longitudinal wave is drawn, and identifying nodes and antinodes.	8
Measuring the speed of sound with an oscilloscope	Recall questions on the signal generator and microphone arrangement, why a two-beam oscilloscope is used, the y-gain and time base, and the main uncertainties.	9
Wavefronts, superposition and phase	Recall questions on what a wavefront is, how wavefronts relate to wavelength, the principle of superposition, and what it means for oscillations to be in phase.	9
Coherence, path difference and phase difference	Recall questions on coherence and why it is needed, why two filament lamps will not interfere, and the relationship between path and phase difference.	9
Interference in practice	Recall questions on the path and phase conditions for constructive and destructive interference, the two-loudspeaker experiment, and whether interference destroys energy.	10
Stationary waves, nodes and antinodes	Recall questions on how a stationary wave forms, node and antinode spacing, the phases either side of a node, and the three ways it differs from a progressive wave.	9
Harmonics on a stretched string	Recall questions on why only certain frequencies fit, the wavelength and frequency of the nth harmonic, and how tension, length and mass per unit length change the first harmonic.	11
Investigating a vibrating string, and air columns	Recall questions on the graphs that confirm the frequency dependences, measuring mass per unit length, locating resonance precisely, and stationary waves in a closed tube.	8
Intensity, the inverse square law and refractive index	Recall questions on the definition and unit of intensity, why it falls as an inverse square, how it depends on amplitude, and the definition of refractive index.	10
Refraction, wave speed and the critical angle	Recall questions on the refraction relationship, which way a ray bends and why, the speed and wavelength in the medium, and the definition of the critical angle.	10
Total internal reflection and measuring refractive index	Recall questions on the two conditions for total internal reflection, sin C = 1/n, and the glass-block experiment with optical pins.	10
Lenses, ray diagrams and the images they form	Recall questions on focal length and the principal axis, the three construction rays, real against virtual images, and the image formed at each object position.	14
Lens power and the thin lens equation	Recall questions on power in dioptres, the sign of a diverging lens, why the powers of thin lenses in contact add, and the real-is-positive convention.	9
Lens calculations and magnification	Recall questions on solving the thin lens equation for converging and diverging lenses, the two expressions for magnification, and what covering half a lens does.	8
Reflection, transmission and the pulse-echo principle	Recall questions on what happens at a boundary, why coupling gel is used, and the relationship a pulse-echo system uses to find a distance.	9
Pulse-echo calculations, resolution and ultrasound	Recall questions on halving the measured time, why an object smaller than the wavelength is invisible, pulse length and resolution, and why the gap between pulses matters.	11
Polarisation and diffraction	Recall questions on plane polarisation and what it shows about light and sound, polarising filters and glare, and the conditions under which diffraction is most pronounced.	12
Single-slit patterns and the diffraction grating equation	Recall questions on Huygens' construction, the single-slit pattern and how it changes with wavelength, and the grating equation with its slit spacing.	10
Grating spectra and measuring wavelength	Recall questions on why grating maxima are sharper than double-slit fringes, the white-light spectrum and how it differs from a prism's, and the laser experiment.	8
Electron diffraction and the de Broglie equation	Recall questions on the electron diffraction arrangement, why rings rather than spots are seen, and the de Broglie equation with the Planck constant.	10
de Broglie calculations and wave-particle duality	Recall questions on finding a de Broglie wavelength from speed or accelerating voltage, why a cricket ball shows no diffraction, and why an electron is not simply a wave.	10
Photons and photon energy	Recall questions on what a photon is, E = hf and its wavelength form, which observations the wave model explains, and which need photons.	9
Models of light and the electronvolt	Recall questions on Newton, Huygens, Young and Einstein, the fundamental conflict between the two models, and the electronvolt and its value in joules.	8
Line spectra and atomic energy levels	Recall questions on emission and absorption spectra, why every element has its own lines, transitions and photon frequency, and why energy levels are negative.	11
The photoelectric effect and Einstein's equation	Recall questions on threshold frequency and work function, Einstein's equation, why the maximum kinetic energy appears in it, and what happens below threshold.	13
Evidence for the photon model and photoelectric calculations	Recall questions on the three features the wave model cannot explain, the gold-leaf demonstration, and the kinetic energy against frequency graph.	12

Waves and Particle Nature of Light is 288 of the 1,616 questions in the guide.Get the guide, £8

How the guide is worked

Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.

Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.

Read the full method, the return schedule and the research behind it.