Waves & Applications
Discover how waves transmit energy and information, from the sound waves we hear to the light waves we see and the radio waves that connect our devices.
In This Section
Introduction to Waves
Waves are disturbances that transfer energy from one place to another without transferring matter. They're all around us—from the sound waves that allow us to hear music to the light waves that let us see the world to the radio waves that connect our wireless devices.
Unlike a ball being thrown, which transfers both energy and matter, waves transfer only energy. The medium (the substance the wave travels through) moves back and forth or up and down, but it doesn't travel with the wave.
Types of Waves
Mechanical Waves
Require a medium to travel through.
- Sound waves (through air, water, solids)
- Water waves (through water)
- Seismic waves (through Earth)
Electromagnetic Waves
Can travel through a vacuum (no medium needed).
- Light waves
- Radio waves
- X-rays, microwaves, etc.
Did You Know?
Waves can travel through space! While sound waves need a medium like air or water to travel through, electromagnetic waves like light can travel through the vacuum of space. That's how sunlight reaches Earth and how we can see distant stars and galaxies.
Wave Properties
All waves, whether they're sound waves, water waves, or light waves, share certain fundamental properties that help us describe and understand them.
Anatomy of a Wave
Key Wave Properties
- Wavelength: The distance between two consecutive crests or troughs.
- Amplitude: The maximum displacement from the rest position (height of crest or depth of trough).
- Frequency: The number of complete waves that pass a point in one second, measured in hertz (Hz).
- Period: The time it takes for one complete wave to pass a point, measured in seconds.
- Wave Speed: How fast the wave travels, calculated as wavelength × frequency.
Wave Behaviors
- Reflection: Waves bounce off surfaces (like light off a mirror or echo of sound).
- Refraction: Waves change direction when entering a new medium (like light through water).
- Diffraction: Waves bend around obstacles or through openings.
- Interference: When waves overlap, they can reinforce (constructive) or cancel (destructive) each other.
- Resonance: When a system vibrates at its natural frequency due to wave input.
Try This!
Experiment with our "Wave on a String" simulation to see how changing amplitude, frequency, and tension affects wave properties.
Try the simulation →Sound Waves
Sound waves are mechanical waves that travel through a medium by compressing and expanding the particles of that medium. They cannot travel through a vacuum, which is why there is no sound in space.
How Sound Waves Work
When an object vibrates, it creates areas of high pressure (compressions) and low pressure (rarefactions) in the surrounding medium. These pressure variations travel as a wave, and when they reach our ears, they cause our eardrums to vibrate, which our brain interprets as sound.
Properties of Sound
Pitch
Determined by frequency. Higher frequency = higher pitch. Humans can typically hear frequencies between 20 Hz and 20,000 Hz.
Volume
Determined by amplitude. Greater amplitude = louder sound. Measured in decibels (dB).
Timbre
The quality or "color" of a sound that distinguishes different instruments or voices playing the same note.
Real-World Connection
Sound travels at different speeds through different media. In air at room temperature, sound travels at about 343 meters per second (767 mph). But in water, it travels at about 1,480 meters per second (3,310 mph), and in steel, it can travel at 5,960 meters per second (13,330 mph)! This is why you can hear a train coming by putting your ear to the railroad track before you can hear it through the air.
Light Waves
Light is a form of electromagnetic radiation that travels as waves. Unlike sound waves, light waves don't need a medium to travel through—they can move through the vacuum of space. Light waves are actually part of a larger family called the electromagnetic spectrum.
Properties of Light
Wave-Like Properties
- Reflection: Light bounces off surfaces, allowing us to see objects.
- Refraction: Light bends when passing between different media (like air to water).
- Diffraction: Light bends around obstacles or through small openings.
- Interference: Light waves can combine to create patterns of brightness and darkness.
- Polarization: Light waves can be oriented in specific directions.
Particle-Like Properties
Light also behaves like particles called photons. This dual nature (wave-particle duality) is a fundamental concept in quantum physics.
As particles, photons:
- Carry specific amounts of energy
- Can be absorbed or emitted by atoms
- Can knock electrons out of atoms (photoelectric effect)
Color
The color of light depends on its wavelength. Visible light ranges from about 380 nanometers (violet) to 740 nanometers (red).
Visible Light Spectrum
Try This!
Explore how light behaves with our "Bending Light" simulation. See how light refracts when passing through different materials and how prisms separate white light into colors.
Try the simulation →Electromagnetic Spectrum
The electromagnetic spectrum is the complete range of electromagnetic radiation, from radio waves with the longest wavelengths to gamma rays with the shortest. Visible light is just a tiny portion of this spectrum that our eyes can detect.
The Electromagnetic Spectrum
Types of Electromagnetic Waves
| Type | Wavelength Range | Uses and Applications |
|---|---|---|
| Radio Waves | 1 mm - 100 km | Broadcasting, communications, radar, navigation |
| Microwaves | 1 mm - 30 cm | Cooking, satellite communications, Wi-Fi, Bluetooth |
| Infrared | 700 nm - 1 mm | Thermal imaging, remote controls, night vision |
| Visible Light | 380 nm - 740 nm | Vision, photography, fiber optics, solar energy |
| Ultraviolet | 10 nm - 380 nm | Sterilization, black lights, detecting forgeries |
| X-rays | 0.01 nm - 10 nm | Medical imaging, security scanning, astronomy |
| Gamma Rays | Less than 0.01 nm | Cancer treatment, sterilizing medical equipment, studying space |
Did You Know?
All electromagnetic waves travel at the same speed in a vacuum—the speed of light, which is approximately 300,000 kilometers per second (186,000 miles per second). That's fast enough to circle Earth about 7.5 times in just one second!
Information Transfer
One of the most important applications of waves is their ability to transfer information. From the sound waves that carry our voices to the radio waves that transmit data to our wireless devices, waves are fundamental to modern communication.
How Waves Carry Information
Modulation
To carry information, a wave's properties are modified or "modulated" in ways that represent the information.
Amplitude Modulation (AM)
The amplitude of the wave is varied to encode information.
Frequency Modulation (FM)
The frequency of the wave is varied to encode information.
Digital Modulation
Information is encoded as discrete values (0s and 1s).
Communication Technologies
- Radio and Television: Use electromagnetic waves to broadcast audio and video.
- Mobile Phones: Use radio waves to transmit voice and data.
- Wi-Fi: Uses microwaves to connect devices to the internet wirelessly.
- Fiber Optics: Uses light waves traveling through glass fibers to transmit data.
- Satellite Communications: Uses radio waves to communicate with orbiting satellites.
Digital Information
Modern communication systems primarily use digital information—data represented as sequences of 0s and 1s (binary code). This digital information can be transmitted using waves in various ways:
Digital Signal Transmission
Binary Data
Wave Representation
Digital signals are more resistant to noise and interference than analog signals, allowing for clearer communication and the ability to detect and correct errors.
Real-World Connection
The internet, which connects billions of devices worldwide, relies on waves to transfer information. When you stream a video, send an email, or browse a website, the data is converted into electromagnetic waves that travel through cables, fiber optics, or wireless connections. These waves carry the digital information that makes up the content you're accessing.
Check Your Understanding
1. What is the main difference between mechanical waves and electromagnetic waves?
Answer: Mechanical waves require a medium to travel through, while electromagnetic waves can travel through a vacuum (no medium needed).
2. What determines the color of visible light?
Answer: The wavelength of the light determines its color. Shorter wavelengths appear violet/blue, while longer wavelengths appear orange/red.
3. Name three ways that waves can be used to transfer information.
Answer: Radio broadcasting, fiber optic internet connections, mobile phone communications, satellite TV, Wi-Fi networks, etc.