GCSE Physics Topic 6: Waves

Introduction to Waves

• Waves transfer energy in the direction they are traveling.
• Waves can be absorbed, transmitted, or reflected.
• Particles vibrate to transfer energy through a medium (material or substance).
• Useful Equations:
  • Time period ( T = \frac{1}{f} )
  • Wave speed ( v = f \times \lambda )

Types of Waves

Transverse Waves

• Characteristics:
  • Amplitude: Height from rest position.
  • Wavelength: Distance between two points on successive waves.
  • Crest/Peak: Top of the wave.
  • Trough: Bottom of the wave.
  • Vibrations are perpendicular to energy transfer direction.
• Examples: Electromagnetic waves, water waves.

Longitudinal Waves

• Characteristics:
  • Vibrations are parallel to the direction of energy transfer.
  • Comprised of compressions and rarefactions.
  • Wavelength: Distance between compressions or rarefactions.
• Examples: Sound waves, seismic shock waves.

Refraction

• Definition: Change in wave direction at the boundary between two mediums.
• Wave Front Diagram: Shows how waves change direction.
  • Normal line is perpendicular to surface.
  • Denser mediums cause waves to bend towards the normal.
• Ray Diagram: Illustrates angle of incidence and refraction.
  • Denser medium: Refraction angle smaller than incidence.
  • Less dense medium: Refraction angle larger than incidence.

Electromagnetic Waves

• Order (from longest wavelength to shortest): Radio, Microwave, Infrared, Visible Light, Ultraviolet, X-rays, Gamma rays.
• Wavelength decreases, frequency increases across spectrum.
• All travel at speed of light (~ (3 \times 10^8 ) m/s).
• Human eye detects only visible light.

Uses of Electromagnetic Waves

• Radio Waves: Radio communication, Bluetooth, TV.
• Microwaves: Microwave ovens, satellites.
• Infrared: Thermal monitoring, heaters.
• Visible Light: Fiber optics.
• Ultraviolet: Sun tans, invisible pens, fluorescent lights.
• X-rays: Medical imaging, radiotherapy.
• Gamma Rays: Medical tracers.

Dangers of Electromagnetic Waves

• High frequency waves (UV, X-rays, Gamma rays) transfer lots of energy and can be harmful.
  • Risks include radiation affecting cells and causing cancer.
• Low frequency waves (Radio waves) mostly pass through tissue without absorption.
• UV radiation from the sun can lead to sunburn and increase cancer risk.
• Safety Tip: Use sunscreen to protect against UV exposure.

Next Topic: Magnetism and Electromagnetism