Wave Propagation and Characteristics

Wave Basics

• A wave is a vibration or disturbance that travels and carries energy.
• Wave propagation refers to the movement of waves, defined by frequency, amplitude, wavelength, and wave speed.
• Wave speed (v) is calculated using the formula: v = f × λ, where f is frequency (in Hz) and λ is wavelength (in meters).
• Factors affecting wave speed include tension, rigidity, density, and temperature of the medium.

Types of Waves

• Waves can be categorized based on the presence of a medium:
  • Mechanical Waves: Require a medium (e.g., sound waves).
  • Electromagnetic Waves: Do not require a medium (e.g., light).
• Waves are also classified by propagation direction:
  • Transverse Waves: Particles vibrate perpendicular to wave direction (e.g., waves on a string).
  • Longitudinal Waves: Particles vibrate parallel to wave direction (e.g., sound waves).

Wave Properties

• Frequency: Number of wave cycles per second.
• Wavelength: Distance between identical points on waves (e.g., crest to crest).
• Amplitude: Maximum displacement from the midline of a wave, not correlated with frequency.
• Wave speed is the product of wavelength and frequency; longer wavelengths correlate with lower frequencies.

Sound Waves

• Sound is a vibrational energy moving through a medium, creating compressions (high pressure) and rarefactions (low pressure).
• Speed of sound varies by medium, fastest in solids due to close molecular proximity, slower in liquids, and slowest in gases.
• Temperature affects sound speed; higher temperatures increase molecular energy, speeding up sound transmission.

Electromagnetic Radiation

• Electromagnetic waves propagate through space, carrying energy at the speed of light, consisting of electric and magnetic components.
• The electromagnetic spectrum includes:
  • Radio Waves: Lowest frequency, used in communications.
  • Microwaves: Used in cooking and communication technologies.
  • Infrared Light: Used for heat and in remote sensing.
  • Visible Light: Light detectable by the human eye.
  • Ultraviolet Light: Can cause skin damage, higher frequency than visible light.
  • X-rays: Used for medical imaging.
  • Gamma Rays: Highest frequency, used in cancer treatment.

Reflection and Refraction

• Reflection: Change in direction of waves upon hitting a surface, described by the law of reflection (angle of incidence equals angle of reflection).
• Refraction: Bending of waves when passing from one medium to another, explained by Snell's Law, relating angles of incidence and refraction to indices of refraction.

Wave Interference

• Constructive Interference: Occurs when waves combine to produce a wave with larger amplitude.
• Destructive Interference: Occurs when one wave's crest cancels another's trough, resulting in reduced amplitude.
• Standing Waves: Formed from the interference of two waves with the same frequency moving in opposite directions.

Doppler Effect

• The Doppler effect describes the change in frequency of waves as the source and observer move relative to each other.
• An ambulance siren demonstrates the effect, producing a higher pitch when approaching and a lower pitch when receding.
• In light, redshift and blueshift indicate galaxies moving away or toward an observer, respectively, providing evidence for the expansion of the universe.

This quiz covers the basics of wave propagation, including frequency, amplitude, wavelength, and wave speed. It also discusses factors that affect wave speed and how to calculate it.