Know that the distance d of a far galaxy can be determined using the brightness of a supernova in that galaxy

IGCSE 0625 – Physics: Core Content & Enrichment

How to Use These Notes

• Each numbered section corresponds to a major syllabus block.
• Core content (required for the exam) is highlighted in bold. Supplementary material (useful for deeper understanding or extended‑answer questions) is in normal font.
• Practical activities are marked “Practical”. They provide the hands‑on experience needed for AO3.
• Key formulas are collected in tables for quick reference.
• End‑of‑section “Practice Questions” give exam‑style examples (AO1–AO3).

1 Motion, Forces & Energy

Learning Objectives

• Distinguish between scalar and vector quantities.
• Calculate speed, velocity and acceleration from distance‑time or velocity‑time graphs.
• Apply Newton’s 2nd law (F = ma) to solve problems involving mass, force and acceleration.
• Understand momentum, impulse and the conservation of momentum in collisions.
• Use the work‑energy‑power relationships to calculate energy transferred, power output and efficiency.
• Interpret pressure and density in fluid contexts.

Key Concepts & Formulas

Practical – Determining Acceleration from a Slope

1. Roll a toy car down an inclined plane of known length L.
2. Measure the time t for the car to travel L using a stopwatch (repeat three times for accuracy).
3. Calculate average speed v = L / t and then acceleration a = 2L / t² (since the car starts from rest).
4. Compare the experimental a with the theoretical value a = g sin θ, where θ is the measured incline angle.

Practice Questions

1. A 2 kg ball is thrown vertically upward with an initial speed of 10 m s⁻¹. Calculate the maximum height reached. (AO2)
2. A 0.5 kg cart collides elastically with a 1 kg cart moving at 2 m s⁻¹. The 0.5 kg cart is initially at rest. Find the final speeds of both carts. (AO3 – use momentum & kinetic‑energy conservation)
3. A 60 W electric kettle boils 0.5 kg of water from 20 °C to 100 °C. The specific heat capacity of water is 4.2 kJ kg⁻¹ K⁻¹. Calculate the time taken, assuming 80 % efficiency. (AO2)

2 Thermal Physics

Learning Objectives

• Explain the particle model of matter and relate temperature to average kinetic energy.
• Apply the ideal‑gas relationship pV = nRT (or pV = constant for a fixed mass of gas at constant temperature).
• Calculate heat energy using specific heat capacity and latent heat.
• Describe the three methods of heat transfer – conduction, convection and radiation – and give everyday examples.
• Perform a simple experiment to determine the specific heat capacity of a metal.

Key Concepts & Formulas

Practical – Determining the Specific Heat Capacity of Aluminium

1. Heat a known mass (≈ 200 g) of water in a calorimeter to a temperature T₁ (measure with a thermometer).
2. Heat an aluminium sample of known mass mₐ in a separate container until its temperature is T₂ (≈ 80 °C).
3. Quickly transfer the hot aluminium into the water, stir gently, and record the highest equilibrium temperature Tₑ.
4. Assuming no heat loss, use: \(mₐ cₐ (T₂‑Tₑ) = mw cw (Tₑ‑T₁)\) to solve for the unknown \(cₐ\) (specific heat of aluminium).

Practice Questions

1. Calculate the amount of heat required to melt 0.5 kg of ice at 0 °C. (L_f = 334 kJ kg⁻¹) (AO2)
2. A sealed syringe contains 1.0 g of air at 300 K and 100 kPa. If the temperature is raised to 600 K while the volume remains constant, what is the final pressure? (AO2 – use p/T = constant)
3. Explain why a metal spoon placed in a hot cup of tea feels hotter than a wooden spoon, referring to thermal conductivity. (AO1)

3 Waves

Learning Objectives

• Define wavelength, frequency, period and wave speed; use the relationship v = f λ.
• Distinguish between transverse and longitudinal waves; give examples (light, sound, water ripples).
• Explain reflection, refraction and diffraction, and apply the laws of reflection and Snell’s law for light.
• Describe the electromagnetic spectrum, focusing on visible light, radio, microwaves and X‑rays.
• Use the lens formula and the mirror equation to locate images formed by concave mirrors and converging lenses.
• Carry out a ripple‑tank experiment to measure the speed of a water wave.

Key Concepts & Formulas

Practical – Measuring Wave Speed in a Ripple Tank

1. Set up a ripple tank with a straight source (e.g., a vibrating bar) producing parallel wave fronts.
2. Measure the distance between successive crests (λ) using a ruler placed over the transparent tank.
3. Use a stopwatch to time how long (Δt) a set of 10 crests travel a known distance (d). Calculate the period T = Δt / 10.
4. Compute the speed v = λ / T and compare with the theoretical value v = √(g λ / 2π) for shallow‑water waves.

Practice Questions

1. A sound wave has a frequency of 500 Hz and a wavelength of 0.68 m in air. Calculate its speed. (AO2)
2. An object 3 cm tall is placed 15 cm in front of a converging lens of focal length 10 cm. Find the image height and state whether the image is real or virtual. (AO2)
3. Explain why a radio signal can pass through walls whereas visible light cannot. (AO1 – reference to EM spectrum and wavelength)

4 Electricity & Magnetism

Learning Objectives

• Define charge, current, potential difference (voltage) and resistance.
• Apply Ohm’s law (V = IR) and the power formula (P = VI) to simple circuits.
• Analyse series and parallel circuits, calculate total resistance and current distribution.
• Understand the magnetic field around a straight current‑carrying conductor (right‑hand rule) and the force on a moving charge (F = qvB sinθ).
• Explain electromagnetic induction (Faraday’s law) and its use in generators and transformers.
• Carry out a circuit‑building practical to verify the relationship between voltage, current and resistance.

Key Concepts & Formulas

Practical – Verifying Ohm’s Law

1. Construct a simple circuit with a variable resistor (rheostat), an ammeter, a voltmeter and a battery.
2. Vary the resistance in several steps, recording the corresponding current (I) and voltage (V) each time.
3. Plot V (vertical axis) against I (horizontal axis). The slope of the straight‑line fit gives the resistance R.
4. Discuss possible sources of error (contact resistance, internal battery resistance, meter loading).

Practice Questions

1. A 12 V battery supplies a current of 3 A to a heater. Calculate the resistance of the heater and the power it dissipates. (AO2)
2. Two resistors, 4 Ω and 6 Ω, are connected in parallel and then in series with a 12 Ω resistor. Find the total resistance of the circuit. (AO2)
3. Explain why a transformer can step up voltage while keeping the total power (ignoring losses) approximately constant. (AO1)

5 Nuclear Physics

Learning Objectives

• Recall the structure of the atom (protons, neutrons, electrons) and the concept of isotopes.
• Distinguish between α, β and γ radiation and identify their penetrating abilities.
• Use the half‑life formula to calculate the remaining quantity of a radioactive sample after a given time.
• Explain the basic principles of nuclear fission and fusion and give real‑world examples (e.g., nuclear power stations, the Sun).
• Discuss the benefits and risks of ionising radiation, including safety measures (lead shielding, distance, time).
• Perform a cloud‑chamber observation of radioactive decay (optional enrichment).

Key Concepts & Formulas

Practical – Determining the Half‑Life of a Radioactive Sample (Enrichment)

1. Place a Geiger‑Müller counter near a weak β‑emitting source (e.g., a small piece of potassium‑40 salt).
2. Record the count rate every minute for at least 30 minutes.
3. Plot count rate (N) versus time (t) on semi‑log paper; the slope gives the decay constant λ.
4. Calculate the half‑life using t½ = ln 2 / λ.

Practice Questions

1. A sample of a radioisotope has a half‑life of 5 years. If the initial activity is 800 Bq, what will be its activity after 15 years? (AO2)
2. Identify which of the following radiations can be stopped by a sheet of paper: α, β, γ. (AO1)
3. Explain why fusion in the Sun releases far more energy per kilogram of fuel than fission of uranium‑235. (AO1 – refer to mass defect and binding energy per nucleon)

6 Space Physics (Core + Extension)

Learning Objectives (Core)

• Describe the Earth’s rotation and its effect on day and night.
• Explain the Earth’s orbit around the Sun and how it produces the seasons.
• Identify the phases of the Moon and the cause of lunar and solar eclipses.
• Recall the main components of the Solar System and their relative distances from the Sun.
• Apply the inverse‑square law for light to simple, practical situations (AO3).

1 The Earth’s Rotation and Day‑Night Cycle

• Earth rotates eastwards once every 24 h (≈ 1 rev day⁻¹).
• Rotation causes the apparent daily motion of the Sun, stars and planets.
• Consequences:

  • Day on the side facing the Sun, night on the opposite side.
  • Apparent movement of the Sun from east to west.

2 The Earth’s Orbit and the Seasons

• Orbit is nearly circular with radius ≈ 1 AU = 1.5 × 10⁸ km.
• Orbital period = 1 year = 365.25 days.
• Axis tilt ≈ 23.5° to the orbital plane.

  • When a hemisphere is tilted toward the Sun it experiences summer; the opposite hemisphere experiences winter.
  • Equinoxes: Sun directly over the equator → equal day and night.
  • Solstices: Sun at greatest angular distance from the equator.

3 Moon Phases and Eclipses

• Moon orbits Earth in 27.3 days (sidereal month) and shows a complete set of phases in 29.5 days (synodic month).
• Phases are caused by the changing Sun–Moon–Earth geometry:

  • New Moon – Moon between Sun and Earth (dark side faces Earth).
  • First Quarter – Half‑illuminated disc.
  • Full Moon – Earth between Sun and Moon (fully illuminated disc).
  • Last Quarter – Opposite half illuminated.

• Eclipses:

  • Solar eclipse – Moon blocks Sun’s light (only at New Moon).
  • Lunar eclipse – Earth’s shadow falls on Moon (only at Full Moon).

4 Structure of the Solar System

5 Practical Demonstration – Inverse‑Square Law (AO3)

Objective: Show that the apparent brightness of a light source falls off as the square of the distance.

1. Equipment: bright LED (known luminous intensity), lux‑meter (or smartphone light‑sensor app), metre‑scale ruler, darkened room.
2. Place the LED on a table. Measure illuminance at 0.5 m, 1 m, 1.5 m and 2 m from the source.
3. Record the readings, calculate the ratio to the 0.5 m reading, and compare with the theoretical 1/d² values.
4. Plot the data on a log‑log graph (log brightness vs. log distance); the slope should be –2.

6 Extension – Determining the Distance to a Far Galaxy Using a Supernova

Why This Is an Extension

The core IGCSE syllabus only requires the inverse‑square law. The material below introduces a modern astronomical technique (standard candles) for interested learners.

Key Concepts (Extension)

• Standard candle: An object with a known absolute luminosity (or absolute magnitude M).
• Type Ia supernova: Thermonuclear explosion of a white dwarf that has reached the Chandrasekhar limit (≈ 1.4 M☉). Its peak absolute visual magnitude is very uniform, ≈ –19.3 mag.
• Inverse‑square law for light: \(b = L / (4\pi d^{2})\) where b is apparent brightness, L the absolute luminosity, d the distance.
• Distance modulus: Relates apparent magnitude (m), absolute magnitude (M) and distance (d in parsecs):

  
  \(m - M = 5\log_{10} d - 5\).

Step‑by‑Step Procedure

1. Measure the apparent magnitude m of the supernova at its peak (provided by the observer).
2. Adopt the standard absolute magnitude M = –19.3 mag (or a calibrated value if supplied).
3. Insert the values into the distance‑modulus equation and solve for d:

   
   \(d = 10^{(m - M + 5)/5}\) pc.

4. Convert the distance to the required unit:

   • 1 pc ≈ 3.26 ly
   • 1 Mpc = 10⁶ pc

Example Calculation

Given: a Type Ia supernova in a distant galaxy has an apparent magnitude m = 22.0.

Distance modulus:

\(m - M = 22.0 - (-19.3) = 41.3\)

Distance:

\(d = 10^{(41.3 + 5)/5} = 10^{9.26}\) pc ≈ 1.8 × 10⁹ pc.

In megaparsecs:

\(d ≈ 1.8 × 10³\) Mpc ≈ 1.8 Gpc.

Typical Values for a Type Ia Supernova

Important Points for Extension Answers

• State that a Type Ia supernova is a standard candle because its absolute magnitude is known.
• Write the distance‑modulus equation and substitute the given m and the standard M.
• Show the algebraic steps clearly; keep track of the exponent.
• Convert the final distance into the unit asked for (pc, Mpc or ly).
• Note (optional) that interstellar extinction is ignored at IGCSE level.

Common Misconceptions (Extension)

• Mixing apparent and absolute magnitude: m varies with distance, M is intrinsic.
• Using the inverse‑square law directly with magnitudes: Magnitudes are logarithmic; the distance modulus must be used.
• Neglecting dust extinction: Real research includes it, but it is omitted for IGCSE calculations.

Suggested Diagram (Extension)

A simple schematic showing Earth (observer) on the left, a distant galaxy with a labelled Type Ia supernova, and arrows indicating light travelling to Earth. Labels for absolute magnitude M, apparent magnitude m and distance d should be included.

Practice Question (Extension)

A Type Ia supernova in a remote galaxy is observed with an apparent magnitude of 24.5. Calculate the distance to the galaxy in megaparsecs. (Use M = –19.3.)

Summary of the Whole Syllabus

The IGCSE 0625 physics syllabus is divided into six major blocks. The notes above provide:

• Core knowledge and formulae for each block, aligned with the assessment objectives (AO1–AO3).
• Practical activities that develop experimental skills required for AO3.
• Enrichment material on extragalactic distance measurement, illustrating how the inverse‑square law is applied in modern astronomy.
• Practice questions that model the style and difficulty of past exam papers.

Use these notes as a study guide, a revision tool, and a basis for classroom experiments. Good luck with your IGCSE physics preparation!