Physics 513
Waves Simulation
Name
Date
Waves Websites
Answer all of the questions right in this packet. Rather than typing in all of the URLs, all of the
links are posted on my Teacher page on Schoolwires. For all of these applets, they have you
manipulating the wavelength. We know that this is really done by manipulating the source
(frequency) or the medium (speed) of the wave but these demos blur that distinction.
Part 1 – Reflection from a Concave Barrier
http://www.youtube.com/watch?v=2CJMT3Qgpr8
This link will take you to a YouTube video of an old black and white film strip. I grant that the
quality is not great.
From 0:00 to 0:45, the video shows the reflection of a circular wave made by a point source off
of a concave, parabolic boundary. What is the most important lesson from this section of the
video?
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
From 0:45 to 1:33, the video shows the reflection of a circular wave made by a point source off
of a concave, CIRCULAR boundary. How are these reflections similar to AND different from
those off of a parabolic boundary?
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
Also during this section, they superimpose a parabola over the semicircle. What point is the
video trying to make?
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
Part 2: The Superposition of two sinusoidal waves
http://www.mhhe.com/physsci/physical/jones/student/olc/graphics/jones3physics_i
/ch15/other/15-11/index.html
Set the two waves so that they have an equal wavelength and equal amplitude and a phase of 0.
Describe the “sum” wave” compared to the component waves
______________________________________________________________________________
______________________________________________________________________________
Change the phase of wave 2 to 180o. Describe what happens and why it happens (look at the two
component waves in relation to each other to explain)
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
Change the phase of wave 2 back to 0o. Change the wavelength of wave 2 to 20. Draw a quick
sketch of the pattern, describe what you see in words and write a brief description of WHY this
is the resulting pattern.
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
Sketch:
Change the wavelength of wave 1 so it is 17 and wave 2 so it is 15. Describe what you see. Draw
a sketch and describe what you see. (By the way, this pattern is known as a beat frequency which
we will discuss later)
______________________________________________________________________________
______________________________________________________________________________
Sketch:
Part 3 – Standing waves.
http://ngsir.netfirms.com/englishhtm/StatWave.htm
Turn the ruler on and move the amplitude slider all the way to the right.
Initially, how far is the source from the boundary? ____________
When the source frequency is 25 Hz, you should see an n= 1 standing wave occurring.
How many nodes are there? ___________
How many antinodes? ______________
What is the wavelength of this wave? _________________________
Calculate what the speed of the wave on this string must be
Increase the source frequency until you find the n = 2 standing wave pattern.
At what frequency does this occur? ________________
How many nodes are there? ___________
How many antinodes? ______________
What is the wavelength of this wave? _________________________
Increase the source frequency until you find the n = 3 standing wave pattern.
At what frequency does this occur? ________________
How many nodes are there? ___________
How many antinodes? ______________
What is the wavelength of this wave? _________________________
Name two other frequencies for which you would expect standing wave patterns to form
______________________________________________________________________________
Pick ANY frequency that you did not look at above. Record here _______________
Click and hold on the ring stand and slide it to the left to find a location that gives a standing
wave. At what length does the pattern occur? ________ This is a n = ______ standing wave.
What is the wavelength? __________________
Sketch the pattern below:
Part 4 – Diffraction
http://ngsir.netfirms.com/englishhtm/Diffraction.htm
In this demo, you will be looking for the DEGREE OF CURVATURE of the diffracted waves. A
high degree of curvature means the central grouping of waves looks closer to a semi-circle than a
straight line and a low degree of curvature means it looks closer to a straight line than a semicircle.
Look at the demo for several different wavelengths. As you increase the wavelength, what is
occurring to the curvature of the diffracted waves?
______________________________________________________________________________
Set the wavelength back to a middling value. Test different slit widths. What occurs to the degree
of curvature of the diffracted waves as the width of the slit is decreased.
______________________________________________________________________________
Part 5 – Interference of water waves/2-D interference
http://ngsir.netfirms.com/englishhtm/Interference.htm
Click on the “Same applet, larger version” link
In this demo, where you see the blurry, grayish lines, waves are being canceled out. The lines
along where destructive interference occurs are called NODAL LINES. Where you see clear
crests (white lines) and troughs (dark lines), that’s where waves are constructively interfering.
These lines are called ANTI-NODAL LINES.
Antinodal lines
Nodal lines
How would you describe the pattern in words?
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
Increase the wavelength. As you increase the wavelength, what happens to
the distance between each adjacent nodal line? ____________________________
The width of each antinodal line? ________________________________
Return the wavelength to the original value. Decrease the source separation. What happens to
the distance between each adjacent nodal line? ____________________________
The width of each antinodal line? ________________________________
If you click on any point in the simulation, it will show waves leaving each of the two sources
and meeting at that point. It shows what each wave is doing at that point by looking at the
vibration of the two blue dots at that point.
Click at several locations on different anti-nodal lines. Try to click in the middle of these lines.
Are the waves in phase or out of phase when they meet? How do you know?
______________________________________________________________________________
______________________________________________________________________________
Why does this make sense based on what you know is happening at an anti-nodal line?
______________________________________________________________________________
______________________________________________________________________________
Click at several locations on different nodal lines. Try to click in the middle of these lines.
Are the waves in phase or out of phase when they meet? How do you know?
______________________________________________________________________________
______________________________________________________________________________
Part 6 – Refraction
http://www.physics.uoguelph.ca/applets/Intro_physics/refraction/LightRefract.html
When the simulation starts, you will see a series of wavefronts in the “white” material moving
into the “gray” material. What’s relevant to know is that the wave moves SLOWER in the gray
material. Also, there is no normal line drawn so you will have to imagine it.
Based on our discussion, what about the picture lets you know the waves were slowing down as
they entered the gray medium?
______________________________________________________________________________
______________________________________________________________________________
On the simulation on the right, you will see the angle of incidence listed (initially it is 30o). A
few boxes below this, you will see the angle of refraction.
With an angle of incidence of 30o, what is the angle of refraction? _________
Increase the angle of incidence by 5o a few times. As you do this, each time the angle of
refraction (circle the correct answer)
Increases but by more than 5o each time
Decreases but by more than 5o each time
Increases by 5o each time
Decreases by 5o each time
Increases but by less than 5o each time
Decreases but by less than 5o each time