09.+Vibrations,+Waves,+and+Sound

= ﻿ // Waves,Vibrations, and Sound // = =// WAVES ARE EVERYWHERE IN NATURE //= = // Sound Waves // = = // Telephone Chord Waves // = = // Stadium Waves // = = // Earthquake Waves // = = // Waves on a String // = = // Sklingy Waves // = = // Visible Light Waves // = = // Radio Waves // = = // Microwaves // = = // Water Waves // = = // Sine Wave // = = = = // What is a Wave? // = =// a wave is a disturbance that travels through a medium from one location to another. //= ** //a wave is the motion of a disturbance// **  ** //Types of Waves// ** ** //Slinky Wave- Let's use a slinky wave as an example.// //When the slinky is stretched from end to end and is held at rest, it assumes a natural position known as the equilibrium or rest position.// To introduce a wave here we must first create a disturbance. ** =// This disturbance would look something like this: //= = =

//** The wave we see here is a Longitudinal Wave . **//


 * The medium particles vibrate parallel to the motion of the pulse. **
 * This is the same type of wave that we use to transfer sound. **

**Transverse Waves ** // **The wave formed here is a SINE wave **. // //[]// =  = ** Anatomy of a Wave ** ** © //We will use a transverse wave to describe this since it is easier to see the pieces.// **  ** © In our wave here the dashed line represents the equilibrium position. ** <span style="font-family: 'Comic Sans MS',cursive;">** © Once the medium is disturbed, it moves away from this position and then returns to it ** <span style="font-family: 'Comic Sans MS',cursive;"> <span style="font-family: 'Comic Sans MS',cursive;">** © //The points A and F are called the CRESTS of the wave.// ** <span style="font-family: 'Comic Sans MS',cursive;">** © //This is the point where the wave exhibits the maximum amount of positive or upwards displacement// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">//A second type of wave is a transverse wave.// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">//We said in a longitudinal wave the pulse travels in a direction parallel to the disturbance.// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">//In a transverse wave the pulse travels perpendicular to the disturbance.// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">// The differences between the two can be seen // **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">//Transverse waves occur when we wiggle the slinky back and forth.// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">//They also occur when the source disturbance follows a periodic motion.// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">//A spring or a pendulum can accomplish this.// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //The points D and I are called the TROUGHS of the wave.// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //These are the points where the wave exhibits its maximum negative or downward displacement.// **


 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //The distance between the dashed line and point A is called the Amplitude of the wave.\// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">// This is the maximum displacement that the wave moves away from its equilibrium. // **


 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //The distance between two consecutive similar points (in this case two crests) is called the wavelength.// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //This is the length of the wave pulse.// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //Between what other points is can a wavelength be measured?// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">Wave frequency **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">// We know that frequency measure how often something happens over a certain amount of time. // **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //We can measure how many times a pulse passes a fixed point over a given amount of time, and this will give us the frequency.// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //Suppose I wiggle a slinky back and forth, and count that 6 waves pass a point in 2 seconds. What would the frequency be?// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //3 cycles / second// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //3 Hz// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //we use the term Hertz (Hz) to stand for cycles per second.// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">Wave Period **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //The period describes the same thing as it did with a pendulum.// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //It is the time it takes for one cycle to complete.// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //It also is the reciprocal of the frequency.// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //T = 1 / f// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //f = 1 / T// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">Wave Speed **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //We can use what we know to determine how fast a wave is moving.// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //What is the formula for velocity?// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //velocity = distance / time// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //What distance do we know about a wave// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //wavelength// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //and what time do we know// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //period// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //so if we plug these in we get// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //velocity =// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">// length of pulse / // **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">// time for pulse to move pass a fixed point // **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //v =// l /// T// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //we will use the symbol// l //to represent wavelength// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //v =// l /// T// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //but what does T equal// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //T = 1 / f// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //so we can also write// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //v = f// l **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //velocity = frequency * wavelength// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">© //This is known as the wave equation.// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;"> © //examples// **

<span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">Wave Behavior **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;"> //The behavior of a wave when it reaches the end of its medium is called the wave’s BOUNDARY BEHAVIOR.// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;"> //When one medium ends and another begins, that is called a boundary.// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">Fixed End **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;"> //One type of boundary that a wave may encounter is that it may be attached to a fixed end.// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">//In this case, the end of the medium will not be able to move.// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">//What is going to happen if a wave pulse goes down this string and encounters the fixed end?// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;"> //Here the incident pulse is an upward pulse.// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;"> //The reflected pulse is upside-down. It is inverted.// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;"> //The reflected pulse has the same speed, wavelength, and amplitude as the incident pulse.// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">Fixed End Animation **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;">Free End **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;"> //Another boundary type is when a wave’s medium is attached to a stationary object as a free end.// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;"> //In this situation, the end of the medium is allowed to slide up and down.// **
 * <span style="color: #000000; font-family: 'Comic Sans MS',cursive; language: en-US;"> //What would happen in this case?// **