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# Mechanical and Electromagnetic Waves

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## Cody Woodcock

on 1 July 2011

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#### Transcript of Mechanical and Electromagnetic Waves

Mechanical vs Electromagnetic Waves
Cody Woodcock
Period I
Science In This Presentation I will be going over two types of waves; Mechanical Waves and Electromagnetic Waves I will first talk about Mechanical Waves What is a mechanical wave? A mechanical wave is a disturbance in matter that carries energy from one place to another Mechanical waves require matter to travel through, this matter is called a medium These mediums can be liquids, solids, or gases How are mechanical waves produced? Mechanical waves are produced when a source of energy causes a vibration to travel through a medium So, What Exactly is a vibration? A vibration is a repeating back-and-forth motion Mechanical waves travel in three different ways, the way a mechanical wave travels is how it is classified How do mechanical waves travel? The first wave is Transvers waves; a wave that causes the medium to vibrate at right angles to the direction in which the wave travels In a transverse wave a wavelength is measured from one crest to another or one trough to another A crest is the highest point of the wave above the rest position; a trough is the lowest point below the rest point The second type of wave is longitudinal waves A longitudinal wave is a wave in which the vibration of the medium is parallel to the direction the wave travels Back and forth motion In longitudinal waves to measure the wavelength you take two identical points in two waves, for example from the beginning of one compression to another A compression is an area where the particles in a medium are spaced close together A rarefaction is an are where the particles in a medium are spread out The third and final wave is Surface Waves A surface wave is a wave that travels along a surface separating two media Up and down Up and Down Motion motion Mechanical waves have periodic motion; a motion that repeats at regular time intervals Properties of Mechanical Waves The time it takes for one motion is called a period All periodic motion has a frequency, a frequency is the number of complete cycles in a given time cycles per seconds are measured in hertz (Hz) Also a wave's frequency is equal to the frequency of the vibrating source that produced the wave I've mentioned wavelengths, but what are they? A wavelength is the distance between a point on one wave and the same point on the next cycle of the wave To find the speed of these waves, the formula would be
Speed = Wavelength * Frequency Amplitude of a wave is the maximum displacement of the medium from its rest position, the more energy a wave has the greater its amplitude Behavior of Waves Reflection
occurs when a wave bounces off a surface that it cannot pass through
(Speed or frequency of wave does not change, but the wave can be flipped upside down) Refraction
The bending of a wave as it enters a new medium at an angle
(When a wave enters a medium at an angle, refraction occurs becuase one side of the wave moves more slowly than the other side) Diffraction
The bending of a wave as it moves around an obstacle or passes through a narrow opening
(A wave diffracts more if it wavelength is large compared to the size of an opening or obstacle) Interference
Occurs when two or more waves overlap and compine together I will be talking about two types of interference Constructive Interference
Occurs when two or more waves combine to produce a wave with a larger displacement Destructive Interference
Occurs when two or more waves combine to produce a wave with a smaller displacement Other Interesting things about mechanical waves Sound Waves are longitudinal waves; compressions and rarefactions that travel through a medium Now To get to the other types of waves; Electromagnetic Waves What are electromagnetic waves? Electromagnetic waves are transverse waves consisting of changing electric fields and changing magnetic fields So, what are electric fields and magnetic fields? An electric field in a region of space exerts electric forces on charged particles; electric fields are produced by electrically charged particles and by changing magnetic fields A magnetic field in a region of space produces magnetic forces; magnetic fields are produced by magnets, by changing electric fields, and by vibrating charges How are electromagnetic waves produced? Electromagnetic waves are produced when an electric charge vibrates or accelerates How do electromagnetic waves travel? Electromagnetic waves, unlike mechanical waves, do not need a medium to travel through Changing elecric field produce changing magnetic field and vice versa this causing the fields to regenerate each other; as the fields regenerate their energy travels in the form of waves Electromagnetic waves can travel through a vacuum, or empty space, as well as through matter The transfer of energy by electromagnetic waves traveling through matter or across space is called Electromagnetic radiation Electromagnetic waves may vary in wavelength and frequency The full range of frequencies of electromagnetic radiation is called the electromagnetic spectrum The spectrum consists of radio waves, infrared rays, visible light, ultraviolent eays, X-rays, and gamma rays Radio waves are used in radio and television technologies, as well as in microwave ovens and radar Infrared rays are used as a source of heat and also to discover area of heat differences Visible lights is used by people to see, help keep them safe, and to communicate with one another Ultraviolet Rays are used in health and medicine, and in agriculture X-rays are used in medicine, industry, and transportation to make pictures of the inside of solid objects Gamma rays are used in the medical field to kill cancer cells and make pictures of the brain, and in industrial as an inspection tool Properties of Electromagnetic waves Electromagnetic radiation behaves like a wave sometimes and like stream of particles sometimes Radio Waves Infrared Rays Visible Light Ultraviolet Rays X-rays Gamma Rays The closer you are to the source of light, the brighter the light appears The speed of light in a vacuum is 3.00 * 10^8 meters per second How do electromagnetic waves behave? When light strike a new medium it can be reflected, absorbed, or transmitted; when light is transmitted it can be refracted, polarized, or scattered Regular Reflection
Occurs when parallel light waves strike a surface and reflect all in the same direction Diffuse Reflection
Occurs when parallel light waves strike a rough, uneven surface, and reflect in many different directions Refraction
A light wave can refract, or bend, when it passes at an angle from one medium into another Polarization
Light with waves that vibrate in only on plane Scattering
Light is redirected as it passes through a medium Light can behave differently depending on the surface it hits If the material is transparent it transmits light, meaning it allows most of the light that strikes it to pass through it If the material is translucent it will scatter light Finally a opaque material either absorbs or reflects all of the light that strikes it The End
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