Lecture Notes: Waves and Their Properties

Introduction

• Waves transfer energy without transferring matter.
• Two types of waves:
  • Transverse Waves: Vibration direction is perpendicular to wave propagation.
  • Longitudinal Waves: Vibration direction is parallel to wave propagation.

Transverse Waves

• Examples: Water waves, seismic secondary waves, slinky waves, electromagnetic waves.
• Demonstration: Shaking a spring up and down.
• Key Features:
  • Crest: Highest peak.
  • Trough: Lowest point.

Longitudinal Waves

• Examples: Sound waves, slinky waves, seismic primary waves.
• Demonstration: Shaking a spring forward and backward.
• Key Features:
  • Compression: Particles close together, high pressure.
  • Rarefaction: Particles far apart, low pressure.

Describing Waves

• Amplitude: Distance from equilibrium to peak, represents energy.
• Wavelength (λ): Distance between consecutive peaks, measured in meters.
• Frequency (f): Number of vibrations per second, measured in hertz (Hz).
• Period (T): Time for one vibration, measured in seconds.
• Speed (v): Distance traveled per unit time, v = λ × f.

Wave Phenomena

Reflection

• When waves hit an obstacle, they are reflected.
• Angle of incidence equals angle of reflection.

Refraction

• Occurs when waves travel through different media.
• Speed change causes wavelength change, frequency remains constant.
• Waves bend towards normal in slow medium, away in faster medium.

Diffraction

• Spreading of waves as they pass through a gap or around obstacles.
• More diffraction when wavelength is similar to gap size.

Light Waves

• Transverse and electromagnetic waves.
• Speed of light: 3 × 10^8 m/s.
• Exhibits reflection, refraction, and diffraction.

Reflection of Light

• Angle of incidence equals angle of reflection.
• Virtual images form behind a plane mirror.

Refraction of Light

• Change in light direction as it enters a different medium.
• Refractive index (n): n = sin(i) / sin(r).

Total Internal Reflection

• Occurs when light travels from denser to less dense medium.
• Critical angle: Angle where refracted angle is 90°.
• Applications: Periscopes, binoculars, optical fibers.

Lenses

• Converging Lens: Focuses parallel rays to a point.
• Diverging Lens: Spreads out parallel rays.
• Real Image: Can be projected, formed by converging lenses.
• Virtual Image: Cannot be projected, appears behind the lens.

Correcting Vision

• Short-sightedness: Corrected with diverging lens.
• Long-sightedness: Corrected with converging lens.

Dispersion of Light

• Separation of white light into colors by a prism.
• Violet bends the most, red bends the least.

Electromagnetic Spectrum

• Range from radio waves to gamma rays.
• Higher frequency = higher energy and ionizing potential.

Uses of Electromagnetic Waves

• Radio waves: Communication.
• Microwaves: Cooking and communication.
• Infrared: Thermal imaging, remote controls.
• Visible Light: Vision, photography.
• UV: Sterilization, tanning.
• X-rays: Medical imaging.
• Gamma rays: Cancer treatment.

Harmful Effects

• High frequency waves can ionize and damage tissue.

Sound Waves

• Longitudinal waves requiring a medium.
• Speed: Faster in solids, slower in gases.

Properties of Sound

• Pitch: Related to frequency.
• Loudness: Related to amplitude.

Ultrasound

• Sound above 20,000 Hz, beyond human hearing.
• Uses: Medical imaging, sonar, cleaning.

This lecture introduces wave properties, behaviors such as reflection/refraction, and specific wave types including light and sound waves, and their applications.