Lecture on Waves, Light, and Sound

Introduction

• Waves transfer energy without transferring matter.
• Two main types: Transverse Waves and Longitudinal Waves.

Types of Waves

Transverse Waves

• Vibration direction is perpendicular to wave propagation.
• Examples: Water waves, seismic secondary waves, Slinky waves, electromagnetic waves.
• Demonstration: Shaking a spring up and down shows wave propagation.
• Key features: Crest (highest point), Trough (lowest point).

Longitudinal Waves

• Vibration direction is parallel to wave propagation.
• Examples: Sound waves, Slinky waves, seismic primary waves.
• Demonstration: Shaking a spring forward and backward.
• Key features: Compression (particles close together), Rarefaction (particles far apart).

Describing Waves

• Amplitude (A): Distance from equilibrium to wave peak; indicates 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.
• Wave Speed (v): Distance traveled per unit time; formula: v = λ × f.

Wave Phenomena

Reflection

• Waves hitting an obstacle reflect; direction changes but speed, wavelength, and frequency remain constant.
• Rules: Angle of incidence = angle of reflection.

Refraction

• Wave speed changes when moving between media, causing bending.
• Demonstration: Ripple tank with shallow and deep water.

Diffraction

• Waves spread out when passing through a gap or around an obstacle.
• More diffraction occurs when the wavelength is similar to the gap size.

Light Waves

• Light is a transverse, electromagnetic wave.
• Speed in vacuum: 3 × 10^8 m/s.
• Exhibits reflection, refraction, and diffraction.

Reflection of Light

• Angle of incidence = angle of reflection.
• Virtual images formed behind mirrors.

Refraction of Light

• Refractive index (n): Ratio of speed of light in vacuum to material.
• Snell's Law: n₁ sin i = n₂ sin r.

Total Internal Reflection

• Occurs when light travels from a denser to a less dense medium.
• Uses: Optical fibers, periscopes, binoculars.

Lenses

• Converging Lenses: Bring parallel rays to a focus.
• Diverging Lenses: Spread out parallel rays.
• Image types: Real (can be projected) and Virtual (cannot be projected).

Sound Waves

• Longitudinal waves, requiring a medium (air, water, solids).
• Speed varies: fastest in solids, slowest in gases.

Characteristics

• Pitch: Related to frequency; higher frequency = higher pitch.
• Loudness: Related to amplitude; larger amplitude = louder sound.

Ultrasound

• Frequencies above 20,000 Hz.
• Applications: Medical imaging, cleaning, sonar.

Electromagnetic Spectrum

• Includes radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays.
• All are transverse waves, travel at the same speed in vacuum.
• Uses vary from communication to medical imaging.

Conclusion

• Understanding waves, light, and sound is crucial in various applications from communication to medical technology.