Mechanical Waves Waves are a disturbance that transfers energy from one molecule to another across space. A medium is the matter that waves travel through. It can be water, air, or even solids.
Types of Mechanical Waves There are three types of mechanical waves: Surface Waves Longitudinal Waves Transverse Waves
Types of Waves Surface Waves Surface waves travel along the surface of two separating mediums. Particles at the surface of a surface wave will rotate in a clockwise manner. See the blue particle below.
Types of Waves Surface Waves If you are swimming in the ocean and a large wave comes by, it does not push you forward, you simply rise up and down as it passes!
Types of Waves Con’t Longitudinal Waves Waves that move in the same direction as the disturbance in the medium 2 main parts Compression Rarefaction
Tsunamis Tsunamis show the effects of longitudinal waves when they retract and then advance. Often a tsunami is preceeded by a retraction of the water before the wall arrives Now the crest arrives, sending a wall of water onto the shore. Here you can see the water drawback (trough) exposing these rocks, with the incoming tsunami in the distance
Types of Waves con’t Transverse Waves Any wave in which the medium moves at right angles to the direction of the wave. 2 main parts Crest (the highest point of the wave) Trough (the lowest point of the wave)
Frequency Frequency The number of waves that pass a point in a given amount of time. Hertz The unit used to measure the frequency. 1 Hz = 1 cycle/sec Frequency is the reciprocal of the period. Freq. = 1 / Period
Period Period The period of a wave represents the time it takes one wave to pass. The period is the opposite of the frequency. Period = 1 / Freq.
Wavelength Wavelength Wavelength is measured from two identical points on wave. Usually measured from crest to crest or trough to trough
Wave Speed Speed How fast or slow the wave is moving. Formula: Speed = Frequency x Wavelength *If the speed of a wave is held constant, then as the frequency goes up, the wavelength goes down.
Wave Speed Continued Wave speed is affected by the medium Waves can travel 770 mph in air (Speed of Sound) But, 2-4 miles per second in solids (10000 mph speed of earthquake)
Earthquakes An earthquake is very similar to sound waves or waves in water. It is a disturbance in the Earth that causes a wave to travel through the solids. They are known as seismic waves.
Amplitude Amplitude The vertical distance between the line of origin and the crest or trough. The more energy a wave has then the greater the amplitude (think of an amplifier in a stereo).
Reflection Reflection When a wave bounces off of a surface. The angle the wave comes in at is equal to the angle the wave goes out at.
Refraction Refraction The bending of light as a result of a change in speed. The wave will slow down when going from a less dense medium to a more dense medium.
Interference Interference Constructive Produces one larger wave Destructive Produces a smaller wave or no wave at all. The green wave in the diagram above and to the left has combined the read and blue waves.
Diffraction Diffraction is the bending of a wave as it passes through an opening or around an object.