IGCSE Physics 0625 – 3.1 General Properties of Waves
3.1 General Properties of Waves
What is a wave?
A wave is a disturbance that travels through a medium (or through empty space) carrying energy from one place to another.
Energy transfer without matter transfer
The defining feature of a wave is that it can transfer energy while the particles of the medium only undergo a temporary displacement and return to their original positions.
In a transverse wave, particles move perpendicular to the direction of wave travel.
In a longitudinal wave, particles move parallel to the direction of wave travel.
Because the particles return to their starting points, there is no net transport of matter.
Key relationships
The speed of a wave (\$v\$) is related to its frequency (\$f\$) and wavelength (\$\lambda\$) by the fundamental wave equation:
\$v = f\,\lambda\$
Where:
\$v\$ = wave speed (m s⁻¹)
\$f\$ = frequency (Hz)
\$\lambda\$ = wavelength (m)
Types of waves
Property
Mechanical Waves
Electromagnetic Waves
Medium required
Yes (solid, liquid, or gas)
No (can travel in vacuum)
Examples
Sound, seismic S‑waves
Light, radio, X‑rays
Typical speeds
\overline{300} m s⁻¹ (sound in air) to several km s⁻¹
≈ 3.00 × 10⁸ m s⁻¹ (speed of light)
Particle motion
Transverse or longitudinal
Transverse only (electric and magnetic fields)
Illustrative diagrams
Suggested diagram: A transverse wave showing crests and troughs, and a longitudinal wave showing compressions and rarefactions.
Common misconceptions
“Waves carry matter.” – The particles only oscillate about an equilibrium position.
“All waves need a medium.” – Electromagnetic waves can propagate in empty space.
“Higher frequency always means faster speed.” – Speed depends on the medium; frequency and wavelength adjust to keep \$v = f\lambda\$.
Summary
Waves transfer energy from one location to another without permanent displacement of matter.
The relationship \$v = f\lambda\$ links speed, frequency, and wavelength.
Mechanical waves need a material medium; electromagnetic waves do not.
Understanding particle motion (transverse vs longitudinal) helps visualize how energy moves through the medium.