I can describe how
waves interact with
their surroundings.
Warm Up 5/19
What is the frequency of a wave on the low E string
of a guitar that has a wavelength of 1.23 meters
and travels at 95.7 m/s?
Wave Interactions
The correct frequency of the low E string is 82.41
Hz, what speed does the wave need to travel at to
have this frequency?
Should the guitar player tighten or loosen the
string?
Wave Interactions
Waves interact with their environment and each
other.
Reflection
Reflection is when a
wave hits an object
and bounces off of it.
Waves interact with their environment through
reflection, refraction, and diffraction.
Refraction
Refraction is when a
wave bends and
changes direction as it
passes from one
medium to another.
Refraction is caused by
a change in speed.
Refraction
Refraction
Diffraction
The angle the light hits the boundary between
the mediums determines how much it refracts.
Diffraction is when a
wave hits an object
and bends around it.
Different colors bend different amounts and can
become spread out.
Interference
Wave Simulation Activity
Waves will also interact with other waves.
This is called interference.
Get out a piece of notebook paperyour thomasscience.appspot.com/sims/waves
You will need:
-A piece of paper to answer questions on
-Something to write with
-Your chromebook
Go to:
thomas-science.appspot.com/sims/waves/
1.
2.
Use the sliders to adjust the properties of the
waves. Then press ‘Show Wave Superposition’.
Use the sliders to adjust the properties of the
waves.
Wave 1:A = 0.6 m
Wave 2:A = 0.3 m
Wave 1:A = 0.2 m
Wave 2:A = 0.6 m
λ=1m
λ=1m
f = 1 Hz
f = 1 Hz
How does the amplitude of the combined wave
compare to the amplitudes of the individual
waves?
λ=4m
λ = 0.2 m
Sketch the combined wave.
f = 1 Hz
f = 1 Hz
Interference
3.
When two waves overlap in the same medium
they ‘stack’ and their amplitudes add together.
Increase the frequency of Wave 1 by 0.1 Hz, and
set both amplitudes to 0.5 m.
Physicists call this superposition.
Wave 1:A = 0.5 m
Wave 2:A = 0.5 m
λ=1m
λ=1m
f = 1.1 Hz
f = 1 Hz
What happens when the crests of one of the
waves lines of with the troughs of the other?
Sketch the resulting wave.
Interference
4.
When the two waves are trying to pull the
medium in opposite directions they can cancel
each other out.
When interference between waves results in a
larger amplitude it is called constructive
interference.
When interference results in a smaller
amplitude it is called destructive interference.
Use the sliders to adjust the properties of the
waves.
Wave 1:A = 0.1 m
Wave 2:A = 0.5 m
λ = 0.1 m
λ=1m
f = 2 Hz
f = 0.1 Hz
Sketch the resulting wave. Do the smaller crests
move slower or faster than the larger crests?
5.
5.
Use the sliders to adjust the properties of the
waves.
Add a new Wave and adjust its properties. Make
sure it is going to the right.
Wave 1:A = 0.1 m
Wave 2:A = 0.5 m
Wave 1:A = 0.1 m
Wave 2:A = 0.5 m
Wave 3:A = 1.0 m
λ = 0.1 m
λ=1m
f = 2 Hz
f = 0.3 Hz
Sketch the resulting wave. Do the smaller crests
move slower or faster than the larger crests?
λ = 0.1 m
λ=1m
λ=4m
Sketch the resulting wave.
f = 2 Hz
f = 0.3 Hz
f = 0.2 Hz
6.
Interfere
Remove Wave 3. Adjust the remaining waves.
Set Wave 1 to move to the left.
Wave 1:A = 0.5 m
Wave 2:A = 0.5 m
λ=1m
λ=1m
f = 0.1 Hz
f = 0.1 Hz
What do you observe about the resulting wave?
You may want to hide waves 1 and 2.
Standing Waves – when interference produces a
wave that appears to stand still.
Node - the point on a standing wave that has an
amplitude of zero (no movement)
Antinode - the point on a standing wave that has
the maximum amplitude (the most movement)
These often occur when a wave is reflected and
interferes with itself.