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

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:

Diagnostic Interpretation

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

Overall Diagnostic Profile

Sum all 10 topic scores (max 240):

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)

Summary

The key principles covered in this topic are linked in the sub-pages above. Focus on understanding the definitions, applying the formulas or frameworks, and evaluating strengths and limitations of each approach.

Worked Examples

Worked examples demonstrating the application of key concepts are covered in the detailed sub-pages linked above.