DSE Physics Diagnostic Guide

Overview

This diagnostic system covers all 10 core topics of the HKDSE Physics examination. Each topic file contains 3 unit tests (single-topic, testing deep understanding) and 3 integration tests (multi-topic, testing synthesis and application). All questions target the upper difficulty band of the DSE specification.

Topic Coverage Map

#	File	Topic	Key Concepts Tested
1	diag-mechanics.md	Mechanics	SUVAT selection, projectile independence, sign conventions, multi-stage motion
2	diag-forces-motion.md	Forces and Motion	N3L pairs, inclined planes, connected objects, friction direction
3	diag-energy-work.md	Energy and Work	Work at angles, power-velocity, efficiency chains, non-conservative forces
4	diag-waves-sound.md	Waves and Sound	Standing waves, intensity/dB, beats, Doppler effect, pipe harmonics
5	diag-optics.md	Optics	Thin lens sign convention, TIR, compound systems, apparent depth
6	diag-waves-optics.md	Waves and Optics	Diffraction, interference, polarization, EM spectrum, thin films
7	diag-electrical-circuits.md	Electrical Circuits	Kirchhoff's laws, internal resistance, potentiometer, RC circuits
8	diag-electricity-magnetism.md	Electricity and Magnetism	Faraday/Lenz laws, transformers, back EMF, electromagnetic braking
9	diag-heat-gases.md	Heat and Gases	Latent heat, gas law units, kinetic theory, adiabatic processes
10	diag-nuclear-physics.md	Nuclear Physics	Half-life, binding energy, decay chains, mass-energy equivalence

Prerequisite Chains

Mechanics (1)
    |
    v
Forces and Motion (2) ---> Energy and Work (3)
    |                           |
    v                           v
Waves and Sound (4) ---> Waves and Optics (6)
    |                           |
    v                           v
Optics (5)                  Electrical Circuits (7)
                                |
                                v
                        Electricity and Magnetism (8)

Heat and Gases (9) -----> Nuclear Physics (10)

Recommended diagnostic order:

1. Foundation tier: Mechanics, Forces and Motion, Energy and Work
2. Waves tier: Waves and Sound, Waves and Optics, Optics
3. Electromagnetic tier: Electrical Circuits, Electricity and Magnetism
4. Thermal/Nuclear tier: Heat and Gases, Nuclear Physics

Grading Rubric

Scoring per Question

Each question is scored on a 4-level scale:

Level	Descriptor	Criteria
4 - Mastery	Complete and correct	Correct final answer, valid method, appropriate units, no significant errors
3 - Proficient	Minor errors only	Correct approach but arithmetic or algebraic slip; or correct answer with incomplete working
2 - Developing	Partial understanding	Correct setup of some equations but unable to complete; or conceptual error in one step
1 - Beginning	Significant gaps	Wrong approach or fundamental misconception; only isolated correct elements
0 - No attempt	Blank or irrelevant	No meaningful physics content

Diagnostic Interpretation

Per-topic score (out of 24: 6 questions x 4 marks each):

Score	Band	Interpretation	Action
22-24	A	Excellent mastery	Move to integration tests of other topics; consider extension work
18-21	B	Good understanding	Review missed questions; focus on specific weak spots
12-17	C	Adequate foundation	Revisit topic notes; practise with standard textbook exercises first
6-11	D	Significant gaps	Study the topic from fundamentals; use worked examples as templates
0-5	U	Major intervention needed	Seek teacher support; start with basic concepts before attempting diagnostics

Overall Diagnostic Profile

Sum all 10 topic scores (max 240):

Total	Band	Recommendation
216-240	5**	Exam-ready for physics; focus on exam technique and time management
180-215	5	Strong candidate; target specific weaker topics for improvement
144-179	4	Solid foundation; systematic topic-by-topic review recommended
108-143	3	Moderate gaps; prioritise foundation-tier topics first
72-107	2	Significant review needed; consider structured study plan
0-71	1	Intensive intervention; work through prerequisite chain from the start

Common Pitfalls by Topic

Mechanics

• Using distance instead of displacement in SUVAT equations
• Forgetting that projectile horizontal velocity is constant
• Wrong sign for $g$ when taking upward as positive
• Choosing the wrong SUVAT equation for the given unknown

Forces and Motion

• Drawing action-reaction pairs on the same body
• Assuming normal force always equals weight
• Getting friction direction wrong (it opposes relative motion, not the applied force)
• Forgetting to include all forces in free-body diagrams

Energy and Work

• Using $W = Fd$ instead of $W = Fd\cos\theta$ for angled forces
• Assuming conservation of energy when non-conservative forces are present
• Confusing efficiency = output/input with input/output
• Forgetting that power $= Fv$ only when $F$ and $v$ are in the same direction

Waves and Sound

• Confusing wave speed with particle velocity
• Misidentifying longitudinal vs transverse waves
• Forgetting that standing waves require specific boundary conditions
• Using amplitude instead of frequency in the wave equation

Optics

• Wrong sign convention in thin lens equation
• Confusing real and virtual images
• Forgetting that total internal reflection requires the ray to go from denser to less dense medium
• Incorrect magnification sign interpretation

Waves and Optics

• Forgetting that diffraction requires gap size comparable to wavelength
• Wrong path difference conditions for constructive/destructive interference
• Assuming polarisation applies to all waves (only transverse)
• Confusing the order of the electromagnetic spectrum

Electrical Circuits

• Confusing current direction with electron flow direction
• Mixing up EMF and terminal PD
• Wrong formula for parallel resistance ($1/R = 1/R_1 + 1/R_2$, not $R = R_1 + R_2$)
• Ignoring internal resistance in calculations

Electricity and Magnetism

• Using the wrong hand rule (Fleming's left vs right)
• Confusing Faraday's law (magnitude) with Lenz's law (direction)
• Forgetting that back EMF reduces motor current
• Wrong transformer equation application

Heat and Gases

• Using Celsius instead of Kelvin in gas law calculations
• Confusing specific heat capacity with latent heat
• Forgetting that $\gamma = C_p/C_v$ differs for monatomic and diatomic gases
• Incorrect adiabatic vs isothermal process identification

Nuclear Physics

• Using $N_0$ instead of $N$ in $A = \lambda N$
• Confusing half-life with mean life
• Misinterpreting the binding energy per nucleon curve
• Forgetting that $E = mc^2$ requires mass to actually be converted (not just present)

Study Strategy

For students scoring Band A or B on a topic:

• Attempt the integration tests in other topics that reference this topic
• Try to create your own multi-topic problems
• Time yourself under exam conditions (approximately 12 minutes per question for DSE)

For students scoring Band C or D on a topic:

• Return to the main topic notes and review systematically
• Work through textbook examples before retrying diagnostic questions
• Focus on understanding WHY each step works, not just memorising procedures

For students scoring Band U on a topic:

• Start with the prerequisite topics in the chain above
• Build up from basic definitions and concepts
• Use the unit tests as learning exercises (read the solution, then attempt similar problems)