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HKDSE Physics Paper 2 Mock (2027): Four Electives, Answer Two, with Answers
TUTORZONE ORIGINAL MOCK PAPER · HKDSE PHYSICS PAPER 2 (ELECTIVES)
Written to the HKEAA 2027 framework: Paper 2 covers the Elective Part, 20% of the subject mark in 1 hour, mixing multiple-choice and structured questions, with each elective carrying 10% of the subject mark and candidates answering two of the four. This paper prints all four electives – 5 MC items plus 1 structured question, 20 marks each, 24 items in all – with worked answers and mark allocation.
What is in HKDSE Physics Paper 2?
Direct answer: Paper 2 covers the Elective Part: 20% of the subject in 1 hour of multiple-choice and structured questions. Each of the four electives (Astronomy and Space Science, Atomic World, Energy and Use of Energy, Medical Physics) carries 10% of the subject mark, and candidates answer two. Paper 1 covers the Compulsory Part at 60% (2 h 30 min, Section A 21% and Section B 39%) and SBA is 20%.
Assessment at a glance (2027)
| Component | Content | Weighting | Duration |
|---|---|---|---|
| Part A: Astronomy and Space Science | Gravity and orbits, stars and galaxies, redshift and the expanding universe; 5 MC + 1 structured question, 20 marks in this paper | 10% | 1 hour (whole paper) |
| Part B: Atomic World | Atomic models and energy levels, the photoelectric effect, wave-particle duality, nanotechnology; 5 MC + 1 structured question, 20 marks in this paper | 10% | 1 hour (whole paper) |
| Part C: Energy and Use of Energy | Energy sources and conversion efficiency, heat pumps, building energy efficiency, transmission and global warming; 5 MC + 1 structured question, 20 marks in this paper | 10% | 1 hour (whole paper) |
| Part D: Medical Physics | Ultrasound imaging, endoscopes and optical fibres, X-rays and radiation protection, hearing and vision correction; 5 MC + 1 structured question, 20 marks in this paper | 10% | 1 hour (whole paper) |
| The rest of the subject (for reference) | Paper 1 covers the Compulsory Part at 60% in 2 hours 30 minutes (Section A multiple-choice 21% of the subject mark, Section B 39%, all compulsory); SBA is 20% | 60% + 20% | 2 h 30 min |
Paper 2 gives you 60 minutes for two parts, 40 marks: aim at about 25 minutes per part and keep 10 minutes to check. Each part turns on one main relation – F = GMm/r² in Part A, hf = ΔE in Part B, efficiency = useful output / total input in Part C and ultrasound depth = v × t / 2 in Part D. Write the arithmetic beside MC items so you can trace a slip, and show the formula in structured questions: it earns marks even when the number is wrong.
How this paper was built
This is a TutorZone original mock paper: every question, answer and mark allocation is our own, not an HKEAA past paper or marking reference. Only the framework figures (Paper 2 at 20% in 1 hour, each elective at 10% of the subject mark, two of four electives, MC plus structured questions) come from the HKEAA 2027 assessment framework and the Physics Paper 2 sample paper.
HKEAA publishes neither a fixed mark split nor a question count per part, so this paper sets its own: 5 MC items (5 marks) plus one structured question (15 marks), 20 marks per elective, and candidates answer two electives (40 marks in total). Every numeric answer was recomputed programmatically.
Pacing
| Section | Marks | Suggested time | What to do first |
|---|---|---|---|
| Part A: Astronomy and Space Science | 10% | about 30 min | Start orbit questions with F = GMm/r² and v = √(GM/r), then substitute |
| Part B: Atomic World | 10% | about 30 min | Convert energies into eV or J first, and write hf = ΔE |
| Part C: Energy and Use of Energy | 10% | about 30 min | Efficiency means useful output over total input; watch the kWh-J conversion |
| Part D: Medical Physics | 10% | about 30 min | Halve the ultrasound time for depth; use 1/f = 1/u + 1/v on lenses |
| The rest of the subject (for reference) | 60% + 20% | outside Paper 2 | Paper 2 is the electives only; do not mix it with Paper 1 compulsory topics |
How should the 60 minutes be split?
Direct answer: two parts, 40 marks – about 25 minutes per part and 10 minutes to check. Start with the part you know better; each part turns on one relation (gravitation in A, hf = ΔE in B, efficiency in C, ultrasound depth in D). Write the relation before substituting, and keep MC arithmetic on the page so you can trace a slip.
Part A: Astronomy and Space Science (5 MC + 1 structured, 20 marks)
Aim at 30 minutes. Attempt only the two electives you studied; all four are printed here so you can compare and self-study.
Question 1
The light year is a unit of which quantity?
A. TimeB. LuminosityC. PowerD. Distance
Question 2
Two point masses attract each other with force F. If their separation is tripled, what is the new force?
A. 9FB. F ÷ 9C. F ÷ 3D. 3F
Question 3
The surface field of the Earth is about 9.81 m s⁻². With a radius of 6.37 × 10⁶ m and G = 6.67 × 10⁻¹¹ N m² kg⁻², what is the mass of the Earth?
A. 5.97 × 10²⁴ kgB. 9.81 × 10²⁴ kgC. 5.97 × 10¹⁸ kgD. 5.97 × 10²⁷ kg
Question 4
A satellite moves to a circular orbit of larger radius. What happens to its orbital speed?
A. UnchangedB. IncreasesC. DecreasesD. First decreases then increases
Question 5
Distant galaxies show a general redshift in their spectra. Which conclusion does this support?
A. Red light travels faster than blue lightB. Galaxies are approaching the Milky WayC. The universe is expandingD. The universe is static
Question 6 (15 marks)
The Moon has a mass of 7.35 × 10²² kg and moves in a circular orbit of radius 3.84 × 10⁸ m around the Earth (mass 5.97 × 10²⁴ kg, G = 6.67 × 10⁻¹¹ N m² kg⁻²). (a) Find the gravitational force on the Moon (3 s.f.); (b) find its orbital speed; (c) hence find the time for one orbit in days (3 s.f.); (d) explain why the gravitational pull does not drag the Moon down to the Earth.
Part B: Atomic World (5 MC + 1 structured, 20 marks)
Aim at 30 minutes. Write ΔE = E_high − E_low first, then convert to J or nm.
Question 1
In Rutherford’s alpha-scattering experiment, most alpha particles pass almost straight through the gold foil. What does this show?
A. The nucleus is negatively chargedB. Electrons are heavier than α particlesC. Atoms are solid spheresD. Most of the space in an atom is empty
Question 2
A metal is lit by light above the threshold frequency. If only the intensity is raised, what changes?
A. The maximum kinetic energy of photoelectrons increasesB. The work function decreasesC. There is no changeD. The number of photoelectrons emitted per second increases, and the maximum kinetic energy of photoelectrons remains unchanged
Question 3
An electron travels at 1.0 × 10⁶ m s⁻¹ (mass 9.11 × 10⁻³¹ kg, h = 6.63 × 10⁻³⁴ J s). What is its de Broglie wavelength?
A. 7.3 × 10⁻⁷ mB. 1.4 × 10⁻⁹ mC. 7.3 × 10⁻¹⁰ mD. 7.3 × 10⁻¹³ m
Question 4
A photon of frequency 5.0 × 10¹⁴ Hz carries about how much energy? (h = 6.63 × 10⁻³⁴ J s, 1 eV = 1.6 × 10⁻¹⁹ J)
A. 2.1 eVB. 4.1 eVC. 1.0 eVD. 0.5 eV
Question 5
The emission spectrum of hydrogen is a line spectrum rather than continuous. Why?
A. A hydrogen atom has only one electronB. Electrons move inside the nucleusC. The energy of electrons in an atom can only take certain discrete valuesD. The temperature of hydrogen is very low
Question 6 (15 marks)
The energy levels of hydrogen are E₂ = −3.40 eV and E₃ = −1.51 eV (h = 6.63 × 10⁻³⁴ J s, c = 3.0 × 10⁸ m s⁻¹, 1 eV = 1.6 × 10⁻¹⁹ J). (a) What photon energy is emitted when an electron falls from E₃ to E₂? (b) Find the wavelength of that photon in nm (3 s.f.); (c) explain why only certain wavelengths are absorbed by a hydrogen atom in its ground state; (d) why do nanomaterials behave differently from the bulk material, and give one application.
Part C: Energy and Use of Energy (5 MC + 1 structured, 20 marks)
Aim at 30 minutes. Show the kW-to-kWh and J-to-kWh conversions inside the working.
Question 1
A lamp takes 60 W and converts 12 W into light, the rest into heat. What is its efficiency?
A. 12%B. 20%C. 48%D. 80%
Question 2
A heat pump has a coefficient of performance of 3.0. How much heat does 1 kWh of electricity deliver indoors?
A. 3 kWhB. 1 kWhC. 6 kWhD. 0.33 kWh
Question 3
Which of the following is NOT a renewable energy source?
A. Solar energyB. Tidal energyC. Natural gasD. Wind energy
Question 4
Electricity is transmitted at very high voltage mainly in order to do what?
A. Reduce electricity consumptionB. Improve power generation efficiencyC. Reduce power loss in transmission linesD. Increase the resistance of transmission lines
Question 5
Compared with solar and wind power, what is the main advantage of nuclear power?
A. The cost of power generation is zeroB. Fuel reserves are unlimitedC. It can supply power steadily and continuously, unaffected by weatherD. There is no radioactive waste
Question 6 (15 marks)
A household electric water heater is rated 2 000 W and runs for 30 minutes a day. (a) Find the energy used in kWh over 30 days; (b) at $1.2 per kWh, find the monthly cost; (c) if a solar hot-water system at 50% efficiency supplies the same heat, how much solar energy input is needed? (d) Suggest two practical ways to cut household energy use and the physics behind each.
Part D: Medical Physics (5 MC + 1 structured, 20 marks)
Aim at 30 minutes. An ultrasound echo travels out and back, so halve the time to get the depth.
Question 1
What frequency do medical ultrasound scanners use?
A. Above 20 GHzB. Below 20 HzC. Above 20 kHz; ultrasound cannot be detected by the human earD. Between 20 Hz and 20 kHz
Question 2
Through which of these media can ultrasound NOT travel?
A. AirB. VacuumC. Soft tissueD. Water
Question 3
Ultrasound travels at about 1 540 m s⁻¹ in tissue. If an echo returns 0.20 ms after the pulse, how deep is the reflecting boundary?
A. 7.7 cmB. 30.8 cmC. 3.1 cmD. 15.4 cm
Question 4
In a short-sighted eye the image of a distant object falls in front of the retina. Which lens corrects it?
A. Convex lensB. Concave lensC. Plane mirrorD. Cylindrical lens
Question 5
Which practice does NOT reduce the radiation dose from an X-ray examination?
A. Shorten the exposure timeB. Increase the voltage of the X-ray tube to increase its penetrating powerC. Use a lead apron for shieldingD. Increase the distance from the radiation source
Question 6 (15 marks)
(a) Explain the basic principle of ultrasound imaging and why it suits prenatal checks better than X-rays; (b) a probe emits 5.0 MHz ultrasound travelling at 1 540 m s⁻¹ in soft tissue – find the wavelength in mm; (c) a short-sighted patient has a far point of 0.5 m – what focal length must the correcting lens have, in dioptres? (d) state two physical requirements for a fibre-optic endoscope to show images from inside the body.
Where are the answers, and do they show the steps?
Direct answer: each part is followed by its own answer section giving the relation, the substitution, the value, the unit and the marks per step (Part A structured question: 4 marks for the force, 4 for the orbital speed, 4 for the period, 3 for the explanation), plus the commonest way to lose each step.
Part A answers and mark allocation
Question 1
Answer: D (Distance) A light year is the distance light travels in a year, about 9.46 × 10¹⁵ m.
Question 2
Answer: B (F ÷ 9) Gravitational force falls with the square of the separation, so tripling it leaves one ninth.
Question 3
Answer: A (5.97 × 10²⁴ kg) From g = GM / R², M = gR² / G = 9.81 × (6.37 × 10⁶)² / 6.67 × 10⁻¹¹.
Question 4
Answer: C (Decreases) v = √(GM / r): a larger radius means a smaller circular-orbit speed, although the period grows.
Question 5
Answer: C (The universe is expanding) A redshift means the galaxies are receding – further galaxies recede faster – which is the evidence for an expanding universe.
Question 6
(a) F = GMm / r² = 6.67 × 10⁻¹¹ × 5.97 × 10²⁴ × 7.35 × 10²² / (3.84 × 10⁸)² = 1.98 × 10²⁰ N (4 marks). (b) The pull supplies the centripetal force: v = √(GM / r) = √(3.98 × 10¹⁴ / 3.84 × 10⁸) = 1.02 × 10³ m s⁻¹ (4 marks). (c) T = 2πr / v = 2π × 3.84 × 10⁸ / 1.02 × 10³ = 2.37 × 10⁶ s ≈ 27.4 days (4 marks). (d) The pull only changes the direction of the velocity, so the Moon is falling towards the Earth all the time, but its tangential speed carries it onwards and the two together keep it in orbit rather than striking the Earth (3 marks).
Part B answers and mark allocation
Question 1
Answer: D (Most of the space in an atom is empty) Only a very few are deflected widely, showing that the positive charge and mass sit in a tiny nucleus.
Question 2
Answer: D (The number of photoelectrons emitted per second increases, and the maximum kinetic energy of photoelectrons remains unchanged) Intensity sets the number of photons per second, hence the number of photoelectrons; the maximum kinetic energy depends on frequency alone.
Question 3
Answer: C (7.3 × 10⁻¹⁰ m) λ = h / (mv) = 6.63 × 10⁻³⁴ / (9.11 × 10⁻³¹ × 1.0 × 10⁶).
Question 4
Answer: A (2.1 eV) E = hf = 6.63 × 10⁻³⁴ × 5.0 × 10¹⁴ = 3.32 × 10⁻¹⁹ J, about 2.07 eV.
Question 5
Answer: C (The energy of electrons in an atom can only take certain discrete values) Electrons jump only between fixed energy levels, emitting photons of definite energy, which gives discrete lines.
Question 6
(a) ΔE = (−1.51) − (−3.40) = 1.89 eV (3 marks). (b) ΔE = 1.89 × 1.6 × 10⁻¹⁹ = 3.02 × 10⁻¹⁹ J, so λ = hc / ΔE = (6.63 × 10⁻³⁴ × 3.0 × 10⁸) / 3.02 × 10⁻¹⁹ = 658 nm (4 marks). (c) Electrons occupy discrete levels, so an incoming photon is absorbed only when its energy exactly matches the gap between two levels; otherwise it passes through (4 marks). (d) Nanomaterials have a huge surface-area-to-volume ratio and a large fraction of surface atoms, plus quantum effects, so melting point, colour and reactivity differ from the bulk (2 marks); examples include titanium dioxide nanoparticles in sunscreens and self-cleaning coatings, or carbon nanotubes for reinforced composites and conductive films (2 marks).
Part C answers and mark allocation
Question 1
Answer: B (20%) Efficiency = useful output / total input × 100% = 12 / 60 × 100%.
Question 2
Answer: A (3 kWh) COP = heat out / electricity in, so the heat delivered is 3.0 × 1 kWh.
Question 3
Answer: C (Natural gas) Natural gas is a fossil fuel and is finite; wind, solar and tidal energy are continuously replenished.
Question 4
Answer: C (Reduce power loss in transmission lines) For the same power, a higher voltage means a smaller current, and the line loss P = I²R falls with the square of the current.
Question 5
Answer: C (It can supply power steadily and continuously, unaffected by weather) Nuclear plants deliver steady output whatever the weather; the drawbacks are radioactive waste and accident risk.
Question 6
(a) Running time = 0.5 h a day, so the energy is 2.0 kW × 0.5 h × 30 = 30 kWh (4 marks). (b) Cost = 30 × $1.2 = $36 (3 marks). (c) Solar input = 30 kWh / 0.5 = 60 kWh (4 marks). (d) Replace filament lamps with LEDs: the same light output costs less input because less energy is wasted as heat (2 marks); thicken the heater’s insulation: less conduction and convection loss, so the water reaches the set temperature in less heating time (2 marks). (Also acceptable: drying clothes in air rather than a tumble dryer, showering instead of bathing, sealing doors and windows against draughts, or setting the air conditioner 1 °C higher.)
Part D answers and mark allocation
Question 1
Answer: C (Above 20 kHz; ultrasound cannot be detected by the human ear) Medical ultrasound runs at megahertz, far above the 20 kHz upper limit of human hearing.
Question 2
Answer: B (Vacuum) Ultrasound is a mechanical wave that needs particles to vibrate, so it cannot cross a vacuum.
Question 3
Answer: D (15.4 cm) The echo travels there and back: depth = v × t / 2 = 1 540 × 0.20 × 10⁻³ / 2 = 0.154 m.
Question 4
Answer: B (Concave lens) A diverging (concave) lens spreads the rays slightly so the focus moves back onto the retina.
Question 5
Answer: B (Increase the voltage of the X-ray tube to increase its penetrating power) Raising the tube voltage hardens the beam and increases penetration; time, distance and shielding are the three protective measures.
Question 6
(a) The probe sends short pulses; at boundaries between tissues of different acoustic impedance part of the wave is reflected, and the return time gives the depth while the echo strength gives the nature of the boundary (3 marks). Ultrasound is a mechanical, non-ionising wave, so unlike X-rays it does not ionise biological molecules and poses less risk to a fetus (2 marks). (b) λ = v / f = 1 540 / 5.0 × 10⁶ = 3.08 × 10⁻⁴ m = 0.31 mm (4 marks). (c) The lens must image a distant object at the far point, so f = 0.5 m and the power is 1 / 0.5 = 2 D (4 marks). (d) Light must undergo total internal reflection at the core-cladding boundary so it is guided without leaking; and the fibre bundle must be ordered (or scanned) so the input and output arrangements match, otherwise the image cannot be reconstructed (2 marks).
Where are Paper 2 marks most easily lost?
Direct answer: four places – orbit answers with no formula, mixing eV with J, forgetting to halve the ultrasound time, and confusing power with energy (W against kWh). Missing units and wrong significant figures cost marks too.
Where these marks are usually lost
| Mistake | What it looks like | What it costs | Instead |
|---|---|---|---|
| Orbit answers with no formula | Writing the speed straight away | Structured marks follow formula, substitution, answer and unit | Write v = √(GM / r) before substituting |
| Mixing eV and J in level calculations | Dividing 1.89 by h as if it were joules | The wavelength comes out wrong by a factor of 10¹⁹ | Convert eV to J with 1.6 × 10⁻¹⁹, then use λ = hc / ΔE |
| Forgetting to halve the ultrasound time | Using v × t for depth | The echo travels out and back, so the depth doubles | Write depth = v × t / 2 and sanity-check the size |
| Confusing power, energy and efficiency | Treating 2 000 W as 2 000 kWh | Power must be multiplied by time, and kWh is not a power unit | Write energy = power × time, then convert to kWh |
How to use this paper
First sit: pick the two electives you study, close the notes and the data sheet, and do the 40 marks in the full 60 minutes.
Mark it: tag every error as formula, substitution or unit; on MC items separate a conceptual slip from an arithmetic one.
Second sit: redo it three to seven days later aiming to write each part’s main relation unaided, with a unit on every value.
What should I do after this paper?
Direct answer: sort your losses into conceptual and arithmetic; drill by elective (orbit calculations, energy levels and the photoelectric effect, efficiency and energy sources, imaging and lenses); then redo the paper in three to seven days and use the Paper 1 mock to keep the compulsory-part rhythm.
FAQ
What is in Paper 2 and how much is it worth?
The Elective Part: 20% of the subject mark in 1 hour, mixing multiple-choice and structured questions, with each elective carrying 10% of the subject mark. Candidates answer two of the four electives (Astronomy and Space Science, Atomic World, Energy and Use of Energy, Medical Physics). Paper 1 covers the Compulsory Part at 60% and SBA is 20%.
Is this an HKEAA paper?
No. The questions, answers and mark allocation are TutorZone originals – not past papers and not an official marking scheme. Only the framework figures come from the HKEAA 2027 assessment framework and the Physics Paper 2 sample paper.
How many questions are there?
HKEAA publishes no fixed count or mark split for Paper 2. This paper sets its own: 5 MC items and one 15-mark structured question per elective (20 marks each, 24 items across four electives); candidates answer two electives, 12 items in practice.
Official references
| Resource | What to check |
|---|---|
| HKEAA 2027 HKDSE Physics Assessment Framework | Confirm Paper 2’s 20% and 1 hour, each elective at 10%, two of four answered, and Paper 1’s 21/39 split |
| https://www.tutorzone.com.hk/en-dse-physics-paper-2-electives-drill-guide/ | Paper 2 electives drilling guide: choosing questions and the one-hour rhythm |
| https://www.tutorzone.com.hk/en-dse-physics-paper-1-mock-2027/ | Paper 1 original mock: Section A MC and Section B structured questions |
| https://www.tutorzone.com.hk/en-dse-physics-past-paper-drill-guide/ | The full physics drilling guide: compulsory against elective revision |
Related: practice area · Paper 2 electives guide · Physics Paper 1 mock
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