Waves Waves as energy Waves as energy Types of waves Types of waves Parts of a wave Parts of a wave Movement of waves Movement of waves Properties of waves Properties of waves

What exactly is a wave? Definition: A wave is any disturbance that transmits energy through matter or space 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 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

So how are these waves different? So how are these waves different? Waves can travels through a medium ( ex. water, ground, air) Waves can travels through a medium ( ex. water, ground, air) Mechanical waves need a medium Mechanical waves need a medium Electromagnetic waves do not 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 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. 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. At the boundary between two media transverse and longitudinal waves can combine to form surface waves. Longitudinal and Transverse Wave Motion Animation courtesy of Dr. Dan Russell, Kettering University

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

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

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.

More Wave Properties Frequency (f) is the number of waves that pass a point in a given time, and measured in hertz. A period (p) is the inverse of frequency = 1/f (time for one wave to pass) 1 23

More Wave Properties The wave speed is measured as distance divided by time. But it can also be calculated by multiplying wavelength by frequency. 1 23

More Wave Movement… When waves bounce off something is it called reflection. 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. When an object or wave hits a surface through which it cannot pass, it bounces back. - Interactions of Waves Reflection

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. 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 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 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 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. 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. 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. Some musical instruments use resonance to produce sound, like a marimba.