Waves
 
 

1. Waves in the Environment:
1. How many kinds of waves are bathing us at this moment?
1. Electromagnetic waves
1. Light waves
1. Visible light
2. Infrared
3. Ultraviolet
2. Radio waves (includes television)
1. Uhf
2. Vhf
3. Vlf
3. X-rays
4. Cosmic Rays
2. Mechanical waves
1. Sound waves
1. Audible sound
2. Ultra sound
3. Subsonic vibrations
2. Ocean waves (Pond ripples)
3. Vibrating bodies (Bridges, springs, strings)
4. Earthquakes
2. We are mainly concerned with light and sound waves that are detectable by unaided human senses. That is visible light and audible sound.
3. How many waves are bathing us at this moment?
2. Draw a wave.
3. http://www.phy.ntnu.edu.tw/java/sound/sound.html Here is a good place to find easy to draw waves and hear them. It is also a good place to start understanding how waves interact. Especially sound waves.
4. Most people draw a sine curve to represent a wave. It is the kind we see most often. It is an example of a transverse wave. There are two basic kinds of waves. Both can be demonstrated with a slinky.
1. Transverse waves (displacement is perpendicular to direction of motion)
1. Snakes, Ocean waves, flags in the breeze, light waves.
2. Longitudinal waves (displacement is parallel to direction of motion)
1. Worms, sound waves, slinkies, plumber's helpers
5. There are actually a couple of other ways of characterizing waves.
1. Standing waves: waves that appear stay in one place like a vibrating violin string.
2. Traveling waves: waves that appear to be moving through space.
6. More wave questions:
1. Where are they coming from?
2. What has happened to them between the time they were generated (created) and now?
3. What will happen to them after now? Do they continue to "live?"
4. These are really questions about how waves behave. What do we know almost instinctively?
1. They travel in space; geometric space. That includes outer space and terrestrial space.
2. They are one way energy is transferred from one place to another.
3. They are affected by the medium in which they travel.
7. Wave Characteristics: How do we measure waves? (very important to the understanding of digital technology)
1. Frequency (Hertz, Hz); a measure of how often per unit of time the wave's motion repeats itself. More often means higher frequency, less often means lower frequency. With light, it is a determinant of color, with sound, a determinant of pitch.
2. Amplitude (Decibel, dB, lux, lumens); a measure of how much a wave changes from one cycle to another. How high are the ocean swells? With light, it is a determinant of brightness, with sound it is a determinant of loudness.
3. Velocity (Meters per second, MPH); a measure of how fast the wave travels in a particular medium. With light, the velocity is constant for a particular medium regardless of the speed of the source. With sound velocity varies with both the medium and the speed of the source (relative to an observer)
8. In media, we are primarily concerned with understanding how waves act in the environment and understanding how we interpret the actions of waves in the environment. Remember all our information comes from our ability to detect changes in the environment; changes that show themselves as waves. Let's begin with some generalizations about what can happen to a wave travelling through "space" when it encounters an object or substance. The characteristics of the wave, the medium, and the object all play a part in each of these actions.
1. Pass through (transmission)
2. Bounce off (reflection)
3. Break up (diffusion)
4. Go around (diffraction)
5. Bend (refraction)
6. Soak in (absorption)
7. Move the object (displacement)
8. Add or Subtract with other waves (interference). Play the antinoise game at http://www.measure.demon.co.uk/Acoustics_Software/anc.html
9.     The interaction of waves, especially sound waves is critical. Play with some of them at http://www.cteh.ac.il/projects/JavaAudio/audio.html
10. Change orientation (polarize)
9. Remember what we learn about light waves applies (with some modifications) to sound waves as well.