Wave Behaviors

Introduction

• Waves are a vital part of everyday life.
• Types of Waves: Mechanical waves and Electromagnetic waves.
• Focus on behaviors: refraction, reflection, transmission, absorption, diffraction, and behavior in different media.

Mechanical Waves: Waves That Need a Medium

• Require a material medium (air, water, solid) to travel.
• Types of Mechanical Waves:
  • Longitudinal Waves: Energy vibrates particles back-and-forth in the same direction as the wave.
  • Transverse Waves: Energy vibrates particles up and down as the wave moves horizontally.
  • Surface Waves: Combination of transverse and longitudinal vibrations.
• Examples: Sound waves, seismic waves, water waves.

Longitudinal Waves

• Energy vibrates particles in a back-and-forth motion.
• Needs a medium (solids, liquids, gases) to transfer energy.
• Characterized by compressions (denser regions) and rarefactions (less dense regions).
• Visible effect: Rice bouncing on speaker due to compressions and rarefactions.

Transverse Waves

• Energy results in perpendicular vibrations to wave direction.
• Examples: Earthquake waves, surface-water waves.
• Visible effect: Shaking a spring toy or plucking a guitar string.

Electromagnetic Waves: Waves That Don't Need a Medium

• Transverse waves that do not require matter.
• Can travel through air, water, solid, and space (vacuum).
• Examples: Light, radio waves.

Electromagnetic Spectrum

• Arrangement of electromagnetic waves by frequency and wavelength.
• Ranges from radio waves to gamma rays.
• Frequency description varies from hertz (radio) to meters (infrared, visible light) to energy (gamma rays).
• Visible light wavelengths: 380 to 740 nm.
• Amplitude perceived as brightness.

Wave Behaviors

• Transmission: Movement through a medium (e.g., sound through ear, light through glass).
• Refraction: Change in direction when passing between media (e.g., light in water).
• Reflection: Bouncing off surfaces (e.g., sound creating echoes, light in mirrors).
• Absorption: Energy conversion into other forms (e.g., sound in foam, light in black surfaces).
• Diffraction: Spreading out after passing through slits or around barriers.

Comparing Mechanical and Electromagnetic Waves

• Both exhibit refraction, reflection, transmission, absorption, diffraction.
• Mechanical waves need a medium; electromagnetic waves do not.

Practical Example: Building a Periscope

• Tool using mirrors to see around objects.
• Fundamental laws of reflection: Angle of incidence equals angle of reflection.
• Materials needed: Long square box, mirrors, protractor, knife, duct tape.
• Educational activity to learn about wave behavior and reflection.