Coffaro 4/20081 Key Terms Wave- traveling disturbance of energy Longitudinal Wave- compression wave; molecules in medium are pushed back and forth parallel to motion Transverse Wave- wave that moves up and down Amplitude- height of wave Wavelength- distance of one wave cycle Frequency- number of waves in a unit of time; measured in Hertz (Hz) Velocity- speed of a wave Medium- substance that allows energy to pass
Coffaro 4/20082 April 8, 2008 Warm Up: Write question and answer. Q: What are the two kinds of waves from the video yesterday? What do waves travel through?
Coffaro 4/20083 Transfer of Energy by Waves MTHS Physical Science
Coffaro 4/20084 What are waves? Mechanical waves are a disturbance in matter that carries energy from one place to another.
Coffaro 4/20085 What do waves require? A medium, or matter to travel through What can act as mediums? Solids, liquids or gases
Coffaro 4/20086 How do we create a mechanical wave? When a source of energy causes a vibration to travel through a medium Ex. When you shake a rope How? Wave that results is vibration that carries energy along the rope What is a Vibration? back and forth motion
Coffaro 4/20087 What are the Types of Mechanical Waves? Transverse Waves Longitudinal Waves Surface Waves
Coffaro 4/20088
9 What are Transverse Waves? A wave that moves up and down This type of wave causes the medium to vibrate at right angles to the direction in which the wave travels Highest point above rest position is called the crest Lowest point below rest position is the trough
Coffaro 4/ Wave diagram
Coffaro 4/ Examples of Transverse Waves Electromagnetic Waves
Coffaro 4/ What are Longitudinal Waves? also called a compression wave because particles in medium are spaced close together molecules in medium are pushed back and forth parallel to motion vibration of the medium is parallel to the direction the wave travels
Coffaro 4/ Examples of Longitudinal Waves Sounds Explosions Earthquakes
Coffaro 4/ What are surface waves? Waves that travel on surface separating two media Most Familiar surface waves are ocean waves
Coffaro 4/ What are the basic characteristics of waves?
Coffaro 4/ What is frequency of a wave? The number of wave cycles in a given unit of time Measured in cycles per second, or Hertz (Hz)
Coffaro 4/ What is the period of a wave? Time required for one cycle, a complete motion, to return to its starting point
Coffaro 4/ What is wavelength of a wave? Distance between a point on one wave and the same point on the next cycle of the wave Increasing frequency decreases wavelength
Coffaro 4/ How do you calculate speed of wave? speed = wavelength x frequency m/s m Hz Example: One end of the rope is vibrated to produce a wave with a wavelength of 0.25 meters. The frequency of the wave is 3.0 Hz. What is the speed of the wave? Wavelength= 0.25 m Frequency= 3.0 Hz Speed= ? Speed = Wavelength x Frequency
Coffaro 4/ What is amplitude of wave? The height of the wave Maximum displacement of medium from rest position The more energy a wave has, the greater is its amplitude
Coffaro 4/ How do waves behave? Reflection Refraction Diffraction Interference
Coffaro 4/ What is reflection? Occurs when wave bounces off surface it can not pass through Does not change speed or frequency of wave, but tends to flip wave upside down
Coffaro 4/200823
Coffaro 4/ What is refraction? Bending of a wave as it enters a new medium at an angle As it enters a medium at angle, refraction occurs because one side of the wave moves more slowly than the other side Only occurs when two sides of wave travel at different speeds
Coffaro 4/200825
Coffaro 4/ What is diffraction? The bending of wave as it moves around an obstacle or passes through a narrow opening Wave diffracts more if its wavelength is large compared to size of opening or obstacle
Coffaro 4/200827
Coffaro 4/ What is interference? Occurs when two or more waves overlap and combine together Two types of interference: Constructive Destructive- occurs when two or more waves combine to produce a wave with smaller displacement
Coffaro 4/ Constructive- occurs when two or more waves combine to produce a wave with a larger displacement
Coffaro 4/ Destructive- occurs when two or more waves combine to produce a wave with smaller displacement