# Waves Waves as energy Types of waves What exactly is a wave? Definition: A wave is any disturbance that transmits energy through matter or space Waves.

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Waves Waves as energy Types of waves

What exactly is a wave? Definition: A wave is any disturbance that transmits energy through matter or space Waves move through matter but they do not move the matter itself Ocean waves Ocean waves Sound waves Sound waves Light waves Light waves Radio waves Radio waves Microwaves Microwaves Earthquake seismic waves Earthquake seismic waves

Waves and Energy Waves travel through water, but they do not carry the water (or the duck) with them.

So how are these waves different? What a wave travels through is called a medium ( ex. water, ground, air) Mechanical waves need a medium Electromagnetic waves do not need a medium

Types of Waves Particles in a transverse wave vibrate in an up and down motion perpendicular to the wave direction. Particles in a compressional wave vibrate back and forth in the same direction that the wave travels. At the boundary between two media transverse and longitudinal waves can combine to form surface waves.

Transverse Waves Waves that move the medium at right angles to the direction in which the waves travel are called transverse waves.

Parts of a Transverse Wave Crest: the highest point Trough: the lowest point

Longitudinal Waves Longitudinal waves move the medium parallel to the direction in which the waves travel.

Surface Waves are combinations of transverse and longitudinal waves. These waves occur at the surface between two mediums, such as water and air. When a wave passes through water, the water (and anything on it) moves up and down, like a transverse wave on a rope. The water also moves back and forth slightly in the direction that the wave is traveling, like the coils of the spring. Surface waves

Compressional Waves Compression: is an area in a wave where the particles are closer together.

Compressional Waves Rarefaction is an area in a wave in which the particles are spread further apart.

Waves Properties of waves

Amplitude, Wavelength, and Frequency The basic properties of all waves are amplitude, wavelength, and frequency.

Amplitude is the height of a wave is and how much energy it is carrying. The wavelength is the distance between crests Properties of Waves Wave simulatorWave simulator courtesy of National Geographic Website

More Wave Properties Frequency is the number of waves that are produced in a given time, and measured in hertz. The wave speed is measured as distance divided by time. But it can also be calculated by multiplying wavelength by frequency. 1 23

Waves Movement of waves

Wave Movement… When waves bounce off something is it called reflection. A reflected sound wave is called an A reflected sound wave is called an echo. echo. When a wave is bent at an angle as it passes through a new medium it is passes through a new medium it is called refraction. called refraction. When a wave is bent around a barrier or an opening it is called diffraction an opening it is called diffraction

When an object or wave hits a surface through which it cannot pass, it bounces back. - Interactions of Waves Reflection

- Interactions of Waves Refraction When a wave enters a new medium at an angle, one side of the wave changes speed before the other side, causing the wave to bend.

- Interactions of Waves Diffraction When a wave moves around a barrier or through an opening in a barrier, it bends and spreads out.

When Waves Interfere with each other… Interference is when two waves overlap. They can overlap and make a larger wave, they can also cancel each other out.

Interference The interference that occurs when waves combine to make a wave with a larger amplitude is called constructive interference. The interference that occurs when waves combine to make a wave with a smaller amplitude is called destructive interference.

- Interactions of Waves Standing Waves If the incoming wave and a reflected wave have just the right frequency, they produce a combined wave that appears to be standing still.

More Wave Properties… When the vibrations of one object cause another nearby to vibrate…that is Resonance. Some musical instruments use resonance to produce sound, like a marimba.

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