Index of wave articles facts for kids

Waves are super cool! They are disturbances that travel through space and time, carrying energy without actually moving matter along with them. Think of a ripple in a pond: the wave moves across the water, but the water itself mostly just bobs up and down. Waves are all around us, from the sound of your voice to the light from the sun, and even the way the ground shakes during an earthquake.

What Are Waves?

A wave is like a messenger that carries energy from one place to another. It's not the stuff itself that moves, but the disturbance in the stuff. Imagine doing "the wave" at a sports game. People stand up and sit down, but they don't actually move around the stadium. The wave of standing and sitting travels around the stadium.

Waves need something to travel through, which we call a medium. For example, sound waves travel through air, water, or solid objects. Light waves are special because they don't need a medium; they can travel through empty space, like from the sun to Earth!

Key Features of Waves

All waves, no matter what kind, have some basic features that help us describe them.

Amplitude: How Big is the Wave?

The amplitude of a wave tells you how "big" or "strong" it is. For water waves, it's how high the crest (top) is or how low the trough (bottom) is from the normal water level. For sound waves, a bigger amplitude means a louder sound. For light waves, it means brighter light.

Wavelength: How Long is One Wave?

The wavelength is the distance between two matching points on a wave, like from one crest to the next crest, or one trough to the next trough. It's like measuring the length of one complete wiggle of the wave. We usually use the Greek letter lambda (λ) to show wavelength.

Frequency: How Many Waves Per Second?

The frequency of a wave tells you how many complete waves pass by a certain point in one second. It's measured in Hertz (Hz). If a wave has a frequency of 10 Hz, it means 10 waves pass by every second. For sound, higher frequency means a higher pitch. For light, different frequencies mean different colors.

Wave Speed: How Fast Does it Travel?

The wave speed is how fast the wave travels through its medium. It's related to wavelength and frequency. Think about it: if waves are longer (bigger wavelength) or if more waves pass by each second (higher frequency), the wave will be moving faster.

Phase: Where is the Wave in its Cycle?

Phase describes where a point on a wave is in its cycle. If two waves are "in phase," their crests and troughs line up perfectly. If they are "out of phase," their crests might line up with the other wave's troughs.

Types of Waves

Waves can be grouped into different types based on how they move or what they travel through.

Mechanical Waves: Needing a Medium

Mechanical waves need a material to travel through. They can't travel through empty space.

• Sound waves are mechanical waves. They are made when something vibrates, like a guitar string or your vocal cords. These vibrations create tiny changes in air pressure that travel to your ears.
• Water waves are also mechanical waves. They travel through water, like the waves you see at the beach.
• Seismic waves are mechanical waves that travel through the Earth during an earthquake. They are what cause the ground to shake.

Electromagnetic Waves: Traveling Through Anything

Electromagnetic waves are special because they don't need a medium to travel. They can zoom through empty space, like the vacuum of outer space, or through air and other materials.

• Light is the most common electromagnetic wave we know. The light from the sun, the light from a lamp, or the light from your phone screen are all electromagnetic waves.
• Radio waves are used for communication, like for radio and TV signals.
• Microwaves are used in microwave ovens to heat food and in radar systems.
• X-rays are used by doctors to see inside your body.
• Gamma rays are very high-energy waves that come from space or nuclear reactions.
• Infrared waves are what we feel as heat.
• Ultraviolet waves are what cause sunburns.

Transverse Waves: Wiggling Sideways

In a transverse wave, the particles of the medium move up and down or side to side, at a right angle to the direction the wave is traveling. Imagine shaking a rope up and down. The wave moves along the rope, but the rope itself moves up and down. Light waves are transverse waves.

Longitudinal Waves: Pushing and Pulling

In a longitudinal wave, the particles of the medium move back and forth in the same direction that the wave is traveling. Think of a Slinky toy: if you push one end, a compression travels along the Slinky. Sound waves are longitudinal waves.

Wave Interactions

Waves don't always travel alone. They can interact with each other and with objects.

Reflection: Bouncing Back

Reflection happens when a wave hits a surface and bounces back. An echo is an example of sound wave reflection. When you look in a mirror, you are seeing light waves reflecting off its shiny surface.

Refraction: Bending Through

Refraction is when a wave changes direction as it passes from one medium to another. This happens because the wave changes speed. If you put a straw in a glass of water, it looks bent because the light waves are refracting as they go from water to air.

Diffraction: Bending Around

Diffraction is when waves bend around obstacles or spread out after passing through an opening. This is why you can hear someone talking around a corner, even if you can't see them. The sound waves bend around the corner.

Interference: Waves Meeting Up

Interference happens when two or more waves meet and combine. They can either add up to make a bigger wave (constructive interference) or cancel each other out (destructive interference). This is how noise-canceling headphones work!

Doppler Effect: Changing Pitch or Color

The Doppler effect is the change in frequency (and thus pitch for sound, or color for light) of a wave as its source moves closer or farther away from you. Think of an ambulance siren: it sounds higher pitched as it comes towards you and lower pitched as it moves away.

Waves in Our Lives

Waves are everywhere and are used in many technologies.

Sound and Hearing

Our ears are designed to detect sound waves. Animals like bats and dolphins use echolocation by sending out sound waves and listening for the echoes to find objects or prey. Ultrasound uses very high-frequency sound waves to create images inside the body, like seeing a baby before it's born.

Light and Seeing

Our eyes detect light waves, allowing us to see the world. Holography uses light waves to create 3D images. Optical fibers use light waves to send information very quickly over long distances, which is how the internet works!

Ocean Waves and Energy

Ocean waves are powerful. Tsunamis are giant ocean waves caused by underwater earthquakes or volcanic eruptions. Rogue waves are unusually large and unexpected waves that can appear in the ocean. We can even use the energy from ocean waves to generate electricity, called wave power.

Brain Waves

Your brain produces electrical signals that create patterns, which scientists call brain waves. Different types of brain waves, like alpha waves or theta waves, are linked to different states of mind, like being awake, relaxed, or asleep.

Seismic Waves and Earthquakes

When an earthquake happens, it sends out seismic waves through the Earth. Scientists use tools called seismographs to detect these waves and study earthquakes. There are two main types of seismic waves: P-waves (primary, longitudinal) and S-waves (secondary, transverse).

Radio and Communication

Radio waves are a type of electromagnetic wave used for broadcasting radio and television, and for wireless communication like Wi-Fi and cell phones. Radar uses radio waves to detect objects and measure their distance and speed.