Chapter 19 - Vibrations and Waves

19.1 - Good Vibrations

Vibrations and waves are fundamental phenomena in physics, describing periodic motions and the transfer of energy through space and time.

• Vibration: A wiggle in time; a periodic motion about an equilibrium position.

• Wave: A periodic wiggle in both space and time, transferring energy from one place to another.

• Sine Curve: A pictorial representation of a wave, showing its oscillatory nature.

19.2 - Wave Description

Waves are characterized by several key properties that describe their motion and behavior.

• Equilibrium Position: The reference point or zero point of a wave.

• Amplitude (A): The maximum displacement from the equilibrium position.

• Wavelength (λ): The distance between successive crests or troughs of a wave.

• Frequency (f): The number of wave cycles per unit time. Units: Hertz (Hz).

• Period (T): The time for one complete vibration.

19.3 - Wave Motion

Wave motion describes how energy is transmitted through a medium via oscillations.

• Transverse Waves: The motion of the medium is perpendicular to the direction of the wave (e.g., light, water waves).

• Longitudinal Waves: The motion of the medium is parallel to the direction of the wave (e.g., sound waves).

• Compression: The part of the medium that is squished together.

• Rarefaction: The part of the medium that is stretched apart.

Examples:

• Transverse: Ripples on the surface of water, vibrations in a string.

• Longitudinal: Sound waves, seismic P-waves, electromagnetic waves (e.g., light, microwaves, radio waves, etc.).

19.4 - Wave Speed

The speed of a wave depends on the medium and the type of wave.

• Wave Speed (v):

• Units: meters per second (m/s)

19.5 - Wave Interference

Interference occurs when two or more waves overlap, resulting in a new wave pattern.

• Superposition Principle: The overlapping of waves.

• Constructive Interference: When waves match up and reinforce each other, resulting in increased amplitude.

• Destructive Interference: When waves are out of sync and cancel each other, resulting in decreased amplitude.

• Standing Wave: A result of constructive interference between an incoming and reflected wave, producing nodes (points of no motion) and antinodes (points of maximum motion).

19.6 - Doppler Effect

The Doppler Effect describes the change in frequency due to the relative motion between a source and an observer.

• Higher Frequency: Observed when moving toward the source.

• Lower Frequency: Observed when moving away from the source.

19.7 - Bow Waves

Bow waves are produced when an object moves faster than the wave speed in a medium, creating a V-shaped pattern.

19.8 - Shock Waves

Shock waves occur when an object moves faster than the speed of sound, resulting in a sudden and loud bang of compressed air (sonic boom).

Chapter 20 - Sound

20.1 - Nature of Sound

Sound is a mechanical wave produced by the vibrations of matter and requires a medium to travel.

• Sound Waves: Longitudinal waves.

• Speed of Sound: In air, about 330 m/s.

• Solids and Liquids: Good conductors of sound.

• Frequency Range: Human hearing: 20 Hz to 20,000 Hz.

20.2 - Sound in Air

• Travels as a longitudinal wave.

• Speed of sound in normal air is about 330 m/s.

• Wave motion of all kinds possesses energy of varying degrees.

20.3 - Reflection of Sound

• Echo: The reflection of a sound wave.

• Angle of reflection equals the angle of incidence.

20.4 - Refraction of Sound

• Refraction is the bending of waves as they transition from one medium to another.

• Occurs because waves travel at different speeds in different mediums.

• Refraction can cause sound waves to bend toward slower mediums.

20.5 - Forced Vibrations

• Occurs when an object starts vibrating because of a nearby vibrating object.

• Natural Frequency: The rate at which an object vibrates naturally.

20.6 - Resonance

• Resonance occurs when the frequency of forced vibrations matches an object's natural frequency, resulting in large amplitude oscillations.

• Energy is transferred efficiently to the system at resonance.

20.7 - Interference

• Interference is the result of superposing different waves.

• Can be constructive or destructive.

20.8 - Beats

• Beats are the periodic variation in the loudness of sound due to interference between two waves of slightly different frequencies.

• Beat Frequency:

Chapter 26 - Properties of Light

26.1 - Electromagnetic Waves

Light is an electromagnetic wave, composed of vibrating electric and magnetic fields.

• Electromagnetic waves travel at the speed of light, m/s.

26.2 - Electromagnetic Wave Velocity

• Electromagnetic waves travel at a constant speed in a vacuum: m/s.

26.3 - Electromagnetic Spectrum

• All electromagnetic waves travel at the speed of light but have different frequencies and wavelengths.

• High frequency waves have shorter wavelengths.

26.4 - Transparent Materials

• Transparent materials allow light to pass through them by absorption and re-emission of energy.

• Materials with higher frequencies require more energy to transmit light.

26.5 - Speed of Light in a Transparent Medium

• Light slows down in transparent materials due to absorption and re-emission.

• Speed of light in glass: m/s.

26.6 - Opaque Materials

• Opaque materials absorb light and convert it to internal energy.

• Light does not pass through opaque materials.

Chapter 27 - Color

27.1 - Color in Our World

Colors are perceived based on the frequency of light that enters our eyes.

27.2 - Selective Reflection

• Some frequencies of light are absorbed, and some are reflected.

• The color we see depends on the light source and the material's properties.

• At resonance, light is absorbed (opaque materials); if not, it passes through (transparent materials).

27.3 - Selective Transmission

• Clear blue glass looks blue because it resonates and absorbs every frequency except blue, which passes through.

27.4 - Mixing Colored Lights

• Additive Primary Colors: Red (R), Green (G), Blue (B).

• Mixing these colors can produce any other color.

• Examples:

  • R + G = Yellow (Y)

  • G + B = Cyan (C)

  • B + R = Magenta (M)

  • R + G + B = White

27.5 - Mixing Colored Pigments

• Subtractive Primary Colors: Cyan (C), Magenta (M), Yellow (Y).

• Mixing pigments subtracts frequencies of light to create colors.

• Examples:

  • C + Y = Green (G)

  • M + Y = Red (R)

  • C + M = Blue (B)

27.6 - Sky Colors

• Particles in the sky scatter blue light more than red light.

• As white light from the sun enters the atmosphere, blue frequencies are scattered, making the sky look blue.

• At sunrise and sunset, sunlight must pass through more atmosphere, scattering blue and leaving red and orange hues.

27.7 - Water Colors

• Water resonates and absorbs more red than blue.

• Subtractive mixing: white light leaves green and blue to be seen, which is the color of bodies of water.

Chapter 29 - Light Waves

29.2 - Diffraction

Diffraction is the bending of waves as they pass the edge of an object or through an opening.

• Diffraction is proportional to the wavelength: longer wavelengths diffract more.

• Diffraction intensity is proportional to the opening size.

29.3 - Superposition and Interference

• Interference can occur with all kinds of waves.

• Superposition principle applies.

29.4 - Single-Color Thin-Film Interference

• Light reflecting off one surface can interfere with light reflected off another surface, producing interference patterns.

• Frequency of light is subtracted out if the path difference is a half-wavelength.

29.5 - Polarization

• Polarization only happens for transverse waves (such as light, not sound).

• Polarization restricts the vibrations of a wave to one direction.

29.6 - Holography

• A hologram is created by the interference of light.