Wave Types, Properties, and Electromagnetic Spectrum

Posted on Mar 23, 2025 in Physics

Types of Waves

Waves can be classified based on several criteria:

A) Type of Energy Propagated

  • Mechanical Waves: These waves propagate mechanical energy caused by a harmonic oscillator. If the wave is harmonic, it’s called a harmonic wave.
  • To produce mechanical waves, you need:
    1. A source of mechanical energy.
    2. A material medium that can be disturbed.
  • Electromagnetic Waves: These waves propagate electromagnetic energy due to oscillations caused by accelerated electric charges.

B) Direction of Propagation and Vibration

  • Longitudinal Waves: The direction of vibration of the particles coincides with the direction of wave propagation.
  • Transverse Waves: The wave propagates perpendicularly to the direction of particle vibration.

C) Number of Dimensions

  • One-Dimensional Waves: Example: A wave on a rope.
  • Two-Dimensional Waves: Example: Waves on the surface of water.
  • Three-Dimensional Waves: Example: Sound waves.

Electromagnetic Spectrum

The electromagnetic spectrum encompasses all radiation of different frequencies that can be decomposed from electromagnetic radiation.

  • Radio Waves: Produced by accelerated electric charges. Used in TV and radio broadcasting.
  • Microwaves: Produced by molecular vibrations. Used in radio astronomy, radar, and microwave ovens.
  • Infrared Radiation: Emitted by hot bodies due to atomic vibrations. Applications in industry, medicine, and TV remote controls.
  • Visible Light: Perceived by the human retina. Produced by electronic jumps between atomic and molecular levels. Colors include red, orange, yellow, green, blue, indigo, and violet.
    Note: Longer wavelengths correspond to lower frequencies, and shorter wavelengths correspond to higher frequencies.
  • Ultraviolet Radiation: Frequencies above violet light. Produced by electronic jumps in excited atoms and molecules. The Sun is a strong emitter; excessive exposure can be dangerous.
  • X-rays: Generated by oscillations of electrons near the nucleus of atoms. Used in industry and medicine. Controlled and rational use is crucial.
  • Gamma Rays: Produced in radioactive phenomena and nuclear reactions. They have great penetrating power and are extremely dangerous to living things. Used in radiation therapy to destroy cancer cells.

Sound

Sound is a mechanical vibration that propagates as waves through any elastic material medium. It requires a medium to propagate and cannot travel through a vacuum. Its longitudinal nature is evident because fluids can transmit it. Sound travels faster in solids than in liquids, and faster in liquids than in gases.

Qualities of Sound

  • Intensity:
    • Physical/Objective: The energy transmitted by the sound wave per unit of time through a surface perpendicular to the propagation direction.
    • Physiological/Subjective: The sensation of varying sound intensity perceived by the human ear.
      • Hearing threshold: 1 x 10-12 dB (decibels)
      • Threshold of pain: 120 dB
  • Pitch:
    • Low-frequency sounds or tones: Low frequency.
    • High-pitched or high tones: High frequency.
  • Timbre: This attribute allows us to distinguish between two sounds of equal intensity and pitch produced by different sources. It depends on the waveform.