General Properties of Waves - IGCSE Physics

Features of Waves

• Energy Transfer:

  • Waves transfer energy without transferring matter.
  • Example: For sound waves, the wave travels while air molecules oscillate around their fixed positions.
  • Evidence: Objects on water (like a floating duck) bob up and down without moving horizontally.

• Oscillations:

  • Waves are described as oscillations or vibrations about a fixed point.
  • Example: Ripples in water cause particles of water to oscillate while not changing their overall position.

Wave Motion

• Vibration Visualization:

  • Can be illustrated through:
  • Vibrations in ropes and springs.
  • Experiments with water waves.

• Ripple Tank:

  • A tool to observe properties such as frequency, wavelength, and wave speed of water waves.

Wave Characteristics

• Important Terms:
  • Wavefront: Represents a single wave, with arrows showing direction and spacing indicating wavelength.
  • Wavelength (λ): The distance from one point on a wave to the same point on the next wave (measured in metres).
  • In transverse waves, measured from peak to peak.
  • In longitudinal waves, from compression to compression.
  • Frequency (f): Number of waves passing a point per second (measured in Hertz (Hz)).
  • Crest: The highest point of a wave above equilibrium.
  • Trough: The lowest point of a wave below equilibrium.
  • Amplitude (A): Maximum displacement from the undisturbed position (measured in metres).
  • Wave Speed (v): The rate at which the wave energy is transferred (measured in m/s).

Wave Equation

• Formula:

  • Wave speed equation: v = f \times \lambda
  • Where:
    • v = wave speed (m/s)
    • f = frequency (Hz)
    • \lambda = wavelength (m)

• Example Calculation:

  • If a wave has a speed of 0.15 m/s and a period of 2 seconds, first calculate frequency:
  1. T = \frac{1}{f} \Rightarrow f = \frac{1}{2} = 0.5 \, \text{Hz}
  2. Use v = f \times \lambda to find wavelength.
     • \lambda = \frac{v}{f} = \frac{0.15}{0.5} = 0.30 \, m

Types of Waves

• Transverse Waves:

  • Vibration direction is perpendicular to wave propagation.
  • Examples include: electromagnetic waves (radio waves, light), water ripples.
  • Cannot travel through fluids. Can travel through solids and vacuums.

• Longitudinal Waves:

  • Vibration direction is parallel to wave propagation.
  • Examples include: sound waves, seismic P-waves.
  • Can travel through solids, liquids, and gases, but not vacuums.

Comparing Waves

• Transverse vs Longitudinal:
  

Reflection and Refraction

• Reflection: Occurs when waves hit a boundary and bounce back without passing through.
• Refraction: Occurs when waves change speed and wavelength when transitioning between media.
  • Frequency remains constant.
  • Change in speed can change direction and wavelength; incident and refracted angles are measured from the normal line.

Diffraction

• Definition: The spreading of waves when they pass through a narrow gap.
  • The extent depends on the gap size relative to the wavelength.
  • Significant diffraction occurs when the gap width is similar to the wavelength, becoming less pronounced with larger gaps.