Wave

这是一篇关于Wave思维导图，概述了波的相关知识，涵盖概述、类型、特性、行为、实验与模拟以及关键术语等方面。

Wave

• Waves Overview
  • A repeating movement/disturbance that transfers energy through matter or space (an oscillation that travels).
  • Principle: All waves carry energy without transporting matter; produced by vibrations; energy passes between neighboring molecules; waves travel as long as there is energy to carry.
• Types of Waves
  • Mechanical Waves-Waves that propagate through a material medium (solid, liquid, gas) at a specific wave speed.
    • Transverse Waves: -Matter moves back and forth at right angles to the wave’s travel direction; e.g., visible light, waves on a string. -Parts: Crest (highest point), Trough (lowest point).
    • Longitudinal Waves: -Matter moves in the same direction as the wave’s travel; e.g., sound waves, seismic waves. -Parts: Compression (matter pushed together), Rarefaction/Expansion (matter spread apart).
    • Speed in Mediums: Fastest in solids, slower in liquids, slowest in gases.
  • Electromagnetic Waves
    • Definition: Waves that do NOT need a medium (matter) to transfer energy; travel through space.
    • Examples: Radiation, TV/radio waves, X-rays, microwaves, lasers, sunlight, visible light.
    • Classification: Considered transverse waves (similar characteristics to transverse mechanical waves).
• Wave Properties
  • Key Characteristics
    • Amplitude: -Definition: Maximum displacement of matter from its equilibrium position (relates to energy). -Unit: Meter (M) -Symbol: A
    • Wavelength: -Definition: Distance from any point on a wave to the same point on the next cycle. -Unit: Meter: (m) -Symbol: λ
    • Frequency: -Definition: Number of wavelengths passing a fixed point per second; how often waves oscillate. -Unit: Hertz (Hz) -Symbol: f
  • Wave Speed
    • Definition: Speed at which a wave moves through a medium (energy transfer speed).
    • Formula: v=f×λ (wave speed = frequency × wavelength); rearranged: λ=v/f, f=v/λ .
    • Example Data: Sound speed in air (20°C): 344 m/s; in water (25°C): 1493 m/s; in diamond: 12000 m/s.
• Wave Behaviors
  • Basic Interactions with Matter
    • Reflection: -Defintion: Wave bounces off an object and travels in a new direction; follows the Law of Reflection (angle of incidence = angle of reflection). -Example: Echo (sound reflection), mirror (light reflection).
    • Refraction: -Definition: Wave bends as it passes into/through a new medium (caused by speed change)greater speed change = more bending. -Example: Pencil looking "broken" in water. -Related Terms: Refractive index (higher in denser mediums: diamond = 2.4, -glass = 1.5, water = 1.30).
    • Diffraction: -Definition: Wave bends around an object or through gaps in an object; more noticeable with narrow gaps. -Example: Sound bending around a wall, light bending through small slits. -Comparison: Refraction = bending through mediums; Diffraction = bending around/through gaps.
    • Absorption: -Defintion: Wave energy is transferred to matter (wave disappears/fades). -Example: Soft materials absorbing sound, black t-shirts absorbing light, plants absorbing light for energy.
  • Wave Interference
    • Definition: When two or more waves overlap and combine to form a new wave.
    • Types: Constructive Interference: Waves add up to create a larger amplitude. -Example: collision of two sound waves with the same frequency but traveling from two different sources Destructive Interference: Waves subtract to create a smaller (or zero) amplitude -Example: noise-canceling headphones.
• Experiments & Simulations
  • Simulations
    • Wave on a String (Phet): Test slow motion/damping effects; observe wave travel.
    • Wave Interference (Phet): Explore diffraction/interference.
    • Virtual Oscilloscope & Tone Generator: Create/hear sounds with different frequencies.
  • Activities
    • Slinky Demonstrations (pairs): Create transverse/longitudinal waves; compare differences.
    • Pendulum Exploration: Link pendulum features to wave properties.
• Key Vocabulary
  • Wave Basics: Oscillation, Vibration, Propagate, Damping (reduces wave energy), Medium (matter through which waves travel).
  • Wave Interactions: Incident waves, Reflected waves, Absorbed waves, Transmitted waves, Scattering.
  • Formulas: Speed equation (v=f×λ).