Waves and Signals

What is a Wave?

• Waves are disturbances that transfer energy from one place to another without moving matter.

• All waves originate from an energy source, typically a vibration.

• Vibration is the back-and-forth or up-and-down motion of an object.

  • Example: Raindrops hitting water create water waves, and vibrating objects like drums or guitar strings generate sound waves.

• Waves continuously transfer energy away from their source.

Mechanical Waves

• Mechanical waves transfer energy without moving matter.

• They travel through solids, liquids, and gases but not in a vacuum.

• Speed:

  • Fastest in solids

  • Slowest in gases

• Examples: Spring waves, sound waves, and ocean waves.

• The medium is the substance through which the wave moves.

Types of Mechanical Waves:

• Transverse Waves

• Longitudinal Waves

Transverse Waves

• A transverse wave is a wave in which the disturbance is perpendicular to the direction of the wave's travel.

  • Example: A flag being blown in the wind.

• Repeating pattern of peaks (crests) and troughs.

• Created when you move the end of a coiled spring up and down; repeated movements transfer energy, creating multiple waves.

• Waves can move even after the object stops vibrating.

Longitudinal Waves

• In longitudinal waves, particles move parallel to the wave's direction.

• These waves create areas where the coils of a spring are closer together (compressions) and areas where they are farther apart (rarefactions).

• Compression: Area where particles are closer together.

• Rarefaction: Area where particles are farther apart.

Sound Waves

• One type of longitudinal wave.

• Travels only through matter.

• Sound travels through air (a mixture of solids and gases) and liquids.

• Sound is caused by vibration. When the door vibrates, the door bumps into nearby air molecules, transferring energy.

• Sound Wave Models: The coiled spring toy demonstrates the properties of longitudinal waves.

Water Waves

• Formed when wind transfers energy to the water.

• They are mechanical waves that move through matter.

• Water waves combine both transverse and longitudinal motion, causing water molecules to move in circular paths that shrink near the ground.

Seismic Waves

• Generated when rocks rapidly shift along a fault, causing an earthquake.

• Seismic waves are a type of mechanical wave, meaning they move through matter, and there are different kinds of seismic waves.

Energy and Amplitude

• A sound wave is longitudinal, and its energy increases with amplitude, similar to transverse waves.

• Amplitude and energy are proportional.

• A low rumble of thunder has less energy and a smaller amplitude than a loud rumble.

• Amplitude is the maximum distance a wave travels from its resting position, and louder vibrations cause waves with greater amplitude.

$energy \propto amplitude^2$

• Wave energy is nonlinear and is the square of the amplitude. Doubling the height results in four times the energy, while halving the height gives a quarter of the energy.

Wavelength

• Wavelength is the distance between corresponding points on consecutive waves.

  • Transverse waves: crest to crest or trough to trough

  • Longitudinal waves: compression to compression or rarefaction to rarefaction

• Wavelength repeats as long as the energy remains constant and is measured in units of distance, such as meters.

Amplitude and Loudness

• The more energy thunder has, the louder it sounds.

• Loudness is how you perceive the energy of a sound wave.

Amplitude, Intensity, and Loudness

• Sound intensity is the amount of sound energy that passes through a square meter of space in one second.

• Sound intensity is measured in decibels (dB), with each 10 dB increase making the sound twice as loud.

• Higher decibel levels reduce the safe listening time to avoid hearing damage.

Wavelength and Frequency

• Frequency is the number of times a wave's pattern repeats within a given time.

• Measured in hertz (Hz).

• 1 Hz = 1 vibration per second.

• Energy of a wave is directly proportional to its frequency.

• Doubling the frequency doubles the energy, and halving the frequency halves the energy.

• Sound frequency and wavelength are inversely related.

• Pitch refers to the perceived highness or lowness of a sound.

Human voices

• 85 Hz to 255 Hz

Thunder

• 20 Hz and 120 Hz.

• Human ear detects sounds between 20 Hz and 20,000 Hz, with frequencies above this range classified as infrasound.

Interactions of Waves with Matter

• Reflection: When a wave hits a barrier, it carries energy and bounces back.

  • The angle at which the wave hits the barrier is equal to the angle at which it reflects.

• Absorption: Occurs when a wave's energy is transferred into the medium it travels through.

• Transmission: The passage of a wave through a medium.

Sound Barriers

• Sound barriers on highways are often made of wood, concrete, or metal.

• The purpose of the barriers is to keep highway noise out of residential areas.

• The higher the wall, the more sound is reflected from the hard surface.

How A Wave Travels Through Matter

• The material or medium affects the speed of sound.

  • Density of the medium.

  • its temperature.
    GAS PARTICLES of a gas are farther apart and collide less frequently than particles of a liquid or solid.
    As temperature of the gas increases, the particles move faster and collide more frequently, transferring more energy in less time.

The Speed of Sound

• Air ($0°C$): 331 m/s

• Air ($20°C$): 343 m/s

• Water ($20°C$) : 1,481 m/s

• Water ($0°C$) : 1,500 m/s

• Seawater ($25°C$) : 1,533 m/s

• Ice ($0°C$) : 3,500 m/s

• Iron : 5,130 m/s

• Glass : 5,640 m/s

Diffraction

• The change in direction of a wave when it travels around the edge of an object or through an opening is called diffraction.

• More diffraction occurs when the size of the object or opening becomes similar in size to the wavelength of the wave.

Light Travel

• Light is electromagnetic radiation that you can see; light is neither matter nor energy but a type of wave.

• Electromagnetic radiation is a type of wave created by vibrating particles.

• Light waves spread out electric and magnetic fields in all directions from the source.

• Radiant energy: is the energy carried by an electromagnetic wave.

Electromagnetic Spectrum

• Radio

• Microwave

• Infrared

• Visible

• Ultraviolet

• X-Ray

• Gamma Ray

• A light wave has a wavelength and a frequency.

• The wavelength of light waves are so short that they measured in nanometers (nm).

• The energy of an electromagnetic wave is related to its frequency. As the frequency increases, the energy of the wave increases.

• Brightness of a light is a person’s perception of intensity.

• Intensity: is the amount of energy that passes through a square meter of space in one second.

• Intensity depends on:

  • Amount of energy a source emits

  • Light’s distance from the source

• As the amplitude of a light wave increases the measured brightness of a wave also increases.

• Some peoples eyes are more sensitive to light than others, and some eyes are more sensitive to colors than others. The environment can also affect the brightness of a light.

• Light, along with the other electromagnetic waves, travels through a vacuum at a speed of about $300,000 km/s$. The speed of light slows down when it travels through matter.

• Light waves travel much faster than sound waves. This explains why you see lighting before you hear thunder.
  Light Travel Properties
  Light travels as waves away from the source.

• Light normally travels in straight lines.

• Light can also spread out slightly as it moves through a small opening.
  Transparent: is a material that allows almost all of the light striking it to pass through and through which objects can be seen clearly.
  Translucent: is a material that allows most of the light that strikes it to pass through, but through which objects appear blurry.
  Opaque: is a material through which light does not pass.
  Reflection: is the bouncing of a wave off a surface.

• Reflected light allows an object to be seen.

• Most types of matter interact with light in a combination of ways.

• As frequency increases, wavelength decreases.

• As the higher the temperature of a star, the more energy it emits.

• White light is made up of different colors, each color has a different range of wavelengths and frequencies.

• Waves with longer wavelengths and lower frequencies travel at greater speeds than waves with shorter wavelengths and higher frequencies.

• Violet wavelength refract the most because their frequencies are the highest.

• Red wavelength have the lowest frequencies and refract the least

• Rainbows form when water droplets in the air function like prisms and refract light.

• Each wavelength of light reflects as it enters the droplet, reflects back into the droplet, and retracts again when it leaves the droplet

• The wavelengths of light near the blue end of the spectrum retract more than wavelengths near the red end of the spectrum.

• Understanding Signals in Communication

• The foundation of modern communication systems

• Signals are defined as variations in physical quantities that convey information. They can represent data in various forms and are crucial to the communication process across different mediums

Signals Types

• Analog signals are continuous in nature, representing information through varying physical quantities. In contrast, digital signals are discrete, representing data as binary values (0's and 1's).

• Significance in information transfer: Signals serve as the main medium through which information is transmitted, allowing devices to communicate and process data efficiently, whether through sound, light, or electromagnetic waves.

Analog Signals Characteristics:

• Analog signals are characterized by their continuous fluctuations, which can take any value within a given range. This trait allows them to faithfully represent real-world phenomena.

  • Everyday analog signals include sound waves, temperature readings from traditional thermometers, and radio waves, all of which exemplify the continuous nature of these signals.

Digital Signal Characteristics:

• Digital signals consist of discrete values usually represented in binary form (Os and 1s). This distinct nature allows for robust error detection and correction techniques in communication.

• Benefits of digital over analog:

  • Digital signals provide numerous advantages such as improved noise resistance, ease of storage, and the ability to transmit multiple signals simultaneously through multiplexing.

Signal Transmissions

• Signals undergo a transmission process where they are converted into a suitable format for travel, whether through wires, air, or fiber optics, before reaching their destination.

Earth motion

• Rotation: A spinning motion

• Rotation axis: The line on which an object rotates

• Orbit: The path an object follows as it moves around another object

• Revolution: The motion of one object around another

• Solstice: A day when Earth's rotation axis is the most toward or away from the sun

• Equinox: A day when Earth's rotation axis is leaning along Earth's orbit, neither toward nor away from the sun

• Rotation refers to the spinning motion of the Earth on its axis.
  The Earth rotates from west to east, completing one full rotation in approximately 24 hours, which gives us the concept of a day and night.

• The rotation is responsible for the rising and setting of the sun, the changing positions of celestial bodies in the sky, and the alternation between daylight and darkness.

• The Earth follows an elliptical path around the sun in a counterclockwise direction (as viewed from above the North Pole).

• The earth's orbital journey is completed in approximately $365.25$ days, which defines a year.

• The axis of Earth's orbit is tilted relative to its axis of rotation, causing the changing seasons as different parts of the Earth receive varying amounts of sunlight throughout the year.

• The sun is lowest in the sky during winter because the Earth's axis is tilted away from the sun.