Wave Properties & Types
Cambridge IGCSE Physics 0625 - Chapter 3: Waves
🌊 The Hook: Earthquake Waves
When an earthquake strikes, seismologists detect two different types of waves. The first wave (P-wave) arrives quickly, shaking the ground back-and-forth. The second wave (S-wave) arrives later, shaking the ground up-and-down. How can the same earthquake produce two completely different wave motions? Understanding wave types could save lives.
📘 Baby Steps: What IS a Wave?
Step 1: Energy Transfer WITHOUT Matter Transfer
Imagine you and your friend hold opposite ends of a rope. You flick your end up and down. A wave travels along the rope to your friend. But notice: the rope itself doesn't travel. Only the energy moves from you to your friend.
KEY PRINCIPLE (Core):
Waves transfer ENERGY from one place to another, but they do NOT transfer MATTER.
Step 2: Two Ways to Vibrate
When energy travels as a wave, the particles of the medium vibrate. But there are only TWO possible directions they can vibrate:
- Perpendicular (90°) to the wave direction → This creates a TRANSVERSE wave
- Parallel to the wave direction → This creates a LONGITUDINAL wave
🔬 Interactive Seismic Wave Visualizer
Use this simulator to see the difference between S-waves (Transverse) and P-waves (Longitudinal). Watch carefully how the ground particles move versus how the wave travels.
Direction of Vibration: Perpendicular (90°) to the direction the wave travels. Particles move UP and DOWN while the wave moves LEFT to RIGHT.
📐 Wave Anatomy: The Essential Terms
Hover over different parts of the wave to see their definitions. These terms are CRITICAL for exam success.
Exam Tip: In Paper 4, you MUST use the correct symbol (λ for wavelength, not "w") and correct units (m, not cm unless specified).
🧮 The Wave Equation: v = fλ
Baby Steps to the Formula:
Step 1: Define Frequency (f)
Frequency is the number of complete waves (or cycles) passing a point per second. Unit: Hertz (Hz). 1 Hz = 1 wave per second.
Step 2: Define Wavelength (λ)
Wavelength is the distance one complete wave occupies. Unit: metres (m).
Step 3: The Logic
If 50 waves pass per second (f = 50 Hz), and each wave is 4 metres long (λ = 4 m), then in one second, the wave has traveled: 50 × 4 = 200 metres. That's the wave speed!
v
Wave Speed
(m/s)
f
Frequency
(Hz)
λ
Wavelength
(m)
⚡ Interactive Speed Calculator
50 complete waves pass a point every second
Each wave occupies 4 metres of space
WAVE SPEED
200 m/s
Calculation: v = 50 Hz × 4 m = 200 m/s
📋 Examples of Wave Types (Core)
TRANSVERSE WAVES
Vibration perpendicular (90°) to direction of energy transfer
- •Light waves (electromagnetic radiation)
- •Water waves (ripples on a pond)
- •Seismic S-waves (secondary earthquake waves)
- •Waves on a string (guitar, rope)
LONGITUDINAL WAVES
Vibration parallel to direction of energy transfer
- •Sound waves (compressions and rarefactions in air)
- •Seismic P-waves (primary earthquake waves)
- •Ultrasound waves (medical imaging)
⚠️ Examiner's Traps: Common Mistakes
TRAP 1: "Waves carry matter"
Wrong: "The wave carries water molecules across the pond."
Correct: "The wave transfers energy across the pond. The water molecules only oscillate up and down."
TRAP 2: Mixing up wavelength and amplitude
Wrong: Measuring wavelength from rest position to crest.
Correct: Wavelength is measured from crest to crest (or any point to the next identical point). Amplitude is measured from rest to crest.
TRAP 3: Forgetting units in calculations
Wrong: "v = 50 × 4 = 200" (no units)
Correct: "v = 50 Hz × 4 m = 200 m/s"
TRAP 4: Confusing transverse and longitudinal
Wrong: "Sound is a transverse wave."
Correct: "Sound is a longitudinal wave because air particles vibrate parallel to the direction of energy transfer."
✅ Syllabus Checklist (Core 3.1.1)
Make sure you can confidently explain ALL of these before moving on:
- ✓Waves transfer energy, NOT matter
- ✓Define: wavefront, wavelength (λ), frequency (f), amplitude, crest, trough
- ✓Distinguish transverse from longitudinal waves
- ✓Give examples: Light, water, S-waves (transverse); Sound, P-waves (longitudinal)
- ✓Use the equation: v = f × λ with correct units
🎓 Lesson Complete!
You've mastered the fundamentals of wave properties. Next up: Wave behavior (reflection, refraction, diffraction).
Sign In to Keep Going
You've reached the end of the free preview. Sign in — and upgrade to Plus or Pro — to keep going with Physics.
Full Access
Unlock all 106 lessons