Waves

1. Definition of Waves

• A wave is a disturbance that transfers energy from one point to another without the transfer of matter.
• Vibrations cause waves, and waves cause vibrations.

2. Types of Waves

a) Transverse Waves

• The disturbance is perpendicular to the direction of wave propagation.
• Examples:
  • Water waves
  • Electromagnetic waves (light, radio waves, X-rays)

b) Longitudinal Waves

• The disturbance is parallel to the direction of wave propagation.
• Examples:
  • Sound waves
  • Compression waves in a slinky

3. Properties of Waves

a) Amplitude $(A)$

• The maximum displacement of particles from their equilibrium position.
• Determines the loudness of a sound wave.

b) Wavelength $(\lambda)$

• The distance between two successive crests or troughs in a transverse wave.
• Measured in metres $(m).$

c) Frequency $(f)$

• The number of complete waves passing a point per second.
• Measured in hertz $(Hz).$
• Determines the pitch of a sound wave and the colour of light.
• Formula: $f = \frac{1}{T}$

where $T$ is the period (time for one wave cycle).

d) Wave Speed (vv)

• The rate at which energy is propagated.
• Formula: $v = f \lambda$

where:

• $v$ $=$ Speed of the wave $(m·s⁻¹)$
• f$$= Frequency $(Hz)$
• $\lambda =$ Wavelength $(m)$

4. Light and the Electromagnetic Spectrum

• Light is part of the electromagnetic spectrum, which includes radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.
• The speed of light in a vacuum is 3.0 × 10^8 m·s⁻¹.
• Colour and Frequency Relationship:
  • Red has the longest wavelength and lowest frequency.
  • Violet has the shortest wavelength and highest frequency.
• Formula for Light: $c = f \lambda$

where:

• $c$ = Speed of light (3.0×10^8 m·s⁻¹)

5. Key Takeaways

✔ Waves transfer energy, not matter.

✔ Transverse waves move perpendicular, longitudinal waves move parallel.

✔ Higher frequency = more energy.

✔ Light waves are part of the electromagnetic spectrum.

Exam Tip

💡 For wave calculations, always check units (convert $km/h$ to $m/s$ if needed)!