Waves in Physics

Waves

• Waves are disturbances that carry energy through matter or space.
• Most waves require a medium to travel through.
• All waves are either mechanical or electromagnetic.
• Mechanical waves need a medium; examples include sound, earthquakes, and tsunamis.
• Electromagnetic waves do not require a medium; examples include light and radio waves.

Energy in Waves

• Energy is the ability to do work.
• Waves carry energy.
• Larger waves carry more energy than smaller waves.
• Energy spreads out as a wave travels outward from its source.

Types of Waves

• Mechanical Waves: waves that require a medium
  • Simple Harmonic Motion: a type of vibration where a force moves a mass back and forth to its original position.
  • Damped Harmonic Motion: a type of vibration fades as energy is transferred .
  • Transverse Waves: waves in which the wave motion is perpendicular to the particle of motion(electromagnetic waves)
    • Crest: top of the wave
    • Trough: bottom of the wave
  • Longitudinal Waves: waves in which the wave motion is parallel to the particle motion
    • Compression: area where the wave is crowded
    • Rarefactions: area where the wave is spread out
  • Surface Waves: waves that occur at the boundary between two different mediums, where the particles move both perpendicular and parallel to the direction of motion.

Wave Properties

• Amplitude: the greatest distance that particles are displaced from their normal resting positions.
• Wavelength: the distance between two consecutive crests or troughs of a wave. Represented by λ (lambda).
• Period: the time required for one complete vibration. Represented by T.
• Frequency: the number of wavelengths that pass a given point in a given time interval. Represented by f (Hertz).
• Wave speed = wavelength * frequency

Wave Behavior

• Doppler Effect: change in frequency of waves due to motion between the source of the waves and the observer.
• Reflection: bouncing back of waves when they meet a surface or boundary. Does not change the wave's speed or frequency.
• Refraction: bending of waves as they pass through an edge or obstacle, depending on wavelength and size of barrier.
• Diffraction: bending of waves as they pass through an edge of an obstacle or narrow opening.
• Interference: combination of two or more waves to form a different resultant wave.
  • Constructive: waves combine to make a bigger wave
  • Destructive: waves combine to make a smaller wave

Sound

• Sound waves are longitudinal waves and mechanical.
• Loudness: response to sound intensity, measured in decibels (dB).
• Intensity: rate at which sound waves transmit energy.
• Pitch: how high or low a sound is, measured by frequency.
• Infrasound: frequencies below the range humans can hear.
• Ultrasound: frequencies above the range humans can hear.

Musical Instruments and Resonance

• Instruments use standing waves.
• Changing features affects wavelength and pitch.
• Resonance is a phenomenon where two objects naturally vibrate at the same frequency.

Light

• Light has a dual nature (wave and particle).

• Light is an electromagnetic wave.

• Photons: packets of energy in light.

• Electromagnetic Spectrum: the range of all possible electromagnetic waves.

• Transparent: materials that allow most light to pass through.

• Translucent: materials that scatter light.

• Opaque: materials that absorb or reflect all light.

• Reflection: light bouncing off a surface. The angle of incidence equals the angle of reflection.

• Mirrors: reflect light. Virtual and real images.

• Lenses: focus or disperse light.

• Refraction: light bending as it passes from one medium to another

• Dispersion: separation of light into its component colors.

• Additive Primary Colors: red, green, and blue—mix to make white light.

• Subtractive Primary Colors: cyan, magenta, and yellow—used in paints, etc. (opposite of additives)