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Target Ideas |
Target
Ideas for Cycle I
1.
Waves have measurable properties such as speed, amplitude, frequency
and wavelength. Speed can be determined by dividing the distance a pulse
travels by the time it takes to travel that distance. Amplitude can be determined by measuring
the maximum motion of the medium. Our
ear interprets amplitude as loudness.
Frequency can be found by measuring the number of waves created or
passing a marker per time period.
Frequency is interpreted by our ears as pitch. Wavelength is the distance between two
positions on a wave with the same displacement, heading the same way. 2.
Speed, frequency and wavelength are independent of amplitude. 3.
Changing the frequency of a wave changes its wavelength
inversely. Changing the medium or the
tension in the medium changes the speed of the wave. 4.
Particles of a medium in which a wave travels may move perpendicular
or parallel to the direction of propagation of the wave. 5.
Waves can change direction when they hit a boundary. If the boundary is rigid, the pulse
experiences a phase inversion. If the
boundary is flexible, the pulse is reflected with the same phase as the
incoming wave. If a pulse strikes the
boundary at an angle, the incoming angle is equal to the reflected angle. 6.
Frequency = velocity/ wavelength 7.
The wave properties discovered in this cycle apply to waves on
springs, water waves, sound waves. 8.
One wavelength (l) is the distance between
three antinodes or 3 nodes. |
Going Into Cycle II: What you need to know.
1. Wave Speed of sound in air is a constant 345
m/sec at sea level and 25oC.
2. Frequency is measured in Hz
(cycles/second). Wavelength is measured
in Meters. That is how wave speed of
sound comes out to be in units of m/sec.
3. When you blow through a musical instrument,
like a flute or a trumpet, and you blow slowly/lightly, you create what is
called the first fundamental. Blow a
little harder and you make the second fundamental (show this demo by blowing into
the pipe harder and harder).
Fundamental frequency is the first frequency needed to set up a standing
wave.
Notice that the frequency increases as
the fundamental increases. But wave
speed (speed of sound) remains 345 m/sec.
What does that mean about wavelength as you increase the
fundamental? (answer: Since frequency is increasing, wave length
must be decreasing)
4. When you look at a wave, here are the parts
of the wave:
Wavelength, Frequency, Node, Antinode
5. When you have an open pipe, the wave exits
the pipe at an antinode (which is a wavecrest or a wavetrough). When you have a closed pipe, the wave exits
the pipe at a node.
6. Questions to think about as you begin this
cycle: What is a note in music? How does it relate to all of this?