Physics 121.6 General Physics
Applets



Here you will find
some applets and other content from the web that will help
you learn some of the most important concepts. Many of them involve
simulations
you can run on your computer. For many of these you will need to be
using
a browser that has "Java" enabled. For some you will need the
"Shockwave"
plugin.
In exercises involving applets, click on
the
"Run
Applet..." link to run the applet. Note: Many applets take some time to
load; up to a minute or so, depending on your connection speed and
network
traffic. (They will in general be loading from somewhere outside
Saskatchewan.)
So be patient, you may be facing a blank box on your screen until the
applet
loads and starts running. After playing with the Applet, click your
browser's
"back" button to return to the Physics 121.6 Applet page.

The following is a list of applet collections that you may find useful.
In the table above however I have links to a few of the many applets
available on the web that I think are most useful in illustrating the
concepts of this course.
Applets 1

Graphs of Position and Velocity
This Applet shows a cow on roller skates! You can
give the cow an initial position, an initial velocity and an initial
acceleration
and then you can see what happened when you click on "RUN". The applet
then draws a position verses time graph and a velocity verses time
graph
of the motion. Note: position is labeled P in the applet rather than x
as we use. Also the applet will not allow you to give a negative
initial
velocity.
Note the shape of the position vs. time graph
and the velocity verses time graph for each of the following cases.
Also
note the green velocity vector that is drawn as the applet runs.
 Try different nonzero initial velocities
with zero
acceleration.
 Try zero initial velocity and nonzero
positive acceleration.
 Try a positive initial velocity and
negative
acceleration.
 Play around with other combinations.
Run
Applet... (After running the Applet, use your
browser's
"back" button to return to this page.)
This second applet displays much the same thing. But as you move the
mouse around you can see how the slope of the position verses time
graph is the velocity and how the slope of the velocity verses time
graph is the acceleration. You can also change the acceleration through
the motion. Try it and see what results...
Run
Applet... (After running the Applet, use your browser's
"back" button to return to this page.)
Applets 2  Vector
Addition
This Shockwave applet shows the addition of two vectors (Red vector +
Green
vector = Blue vector). You can move the Red and Green vectors around
and
change their direction and size and see the resultant Blue vector.
 Notice the components of the vectors are displayed at the top of
the
display;
labeled "Rectangular coordinates". (The first number is the xcomponent
and the second number is the ycomponent.) Check that the components of
the Blue vector components are equal to the sum of the Red and Green
vector
components.
 The magnitude and direction of each vector is also given; labeled
"Polar
coordinates". (The first number is the magnitude and the second
number
is the angle counterclockwise from the +x axis direction.) Check that
the
magnitude and direction given are correct given the components.
Run
Applet...
(After running the Applet, use your browser's "back" button to return
to
this page.)
Another applet which shows much the same thing in a slightly
different
way....
Run
Applet...
(After running the Applet, use your browser's "back" button to return
to
this page.)
Applets 3  Projectile
Motion
This Applet shows the path of a cannonball fired into the air over
a horizontal ground. You can change the initial speed of the
cannonball,
the angle at which the cannonball is fired, and the mass of the
cannonball.
Suggested exercises using the Applet appear with the applet itself.
Run Applet... (After
running the Applet, use your browser's "back" button to return to
this page.)
Here is another applet showing projectile motion with no air
resistance. In this one you can also change the height of the launch
position.
Run
Applet... (After running the Applet, use your browser's "back"
button to return to
this page.)
Applets 4  Circular
Motion
This applet shows the development of the idea that the centripetal
acceleration points toward the centre of the circle. The position
vector of an object moving in a circle at a constant speed at time
intervals. You can successively show the position vector r, the
displacement dr, the instantaneous velocity v, the
change in velocity vector dr, and the acceleration a.
You will see that a points in the opposite direction to r.
Run
Applet... (After running the Applet, use your browser's "back"
button to return to
this page.)
Applets 5  Relative
Motion
This
applet demonstrates relative motion. You can dynamically change the
speed of the boat and the direction of the boat (as well as the speed
of the river. See how the velocity of the boat relative to the bank
changes as you change these parameters.
Run
Applet.... (After running the Applet, use your browser's "back"
button to return to
this page.)
This applet also demonstrates relative motion. It can show the motion
of a
boat in a flowing river, and a man who walks along the bank or swims
through the water. By moving the mouse you can see the motions relative
to difference frames of reference. Read the instructions to see how to
change the velocities of the boat, water or man. Note that velocities
can only be changed when the motion is suspended by clicking the right
mouse button.
Run Applet... (After running the Applet, use your browser's "back"
button to return to
this page.)
The applet shows what motion would look like from a rotating frame of
reference (a noninertial frame). From the point of view of the
rotating frame of reference it appears that there are
fictitious force at play, the Centrifugal force and the Coriolis Force.
Run
Applet... (After running the Applet, use your browser's "back"
button to return to
this page.)
Applets 6  Forces and
Newtons Laws
This applet show a box on an inclined plane. You can change the
mass of the box and the angle of the plane (labeled phi in "Grad" but
it is actually degrees). You can also change the coefficients of
friction between the box and the plane (labeled "Reib" in the applet).
Start with no friction  i.e. make the coefficients zero. Calculate the
acceleration you expect and see that the applet give the expected
result. Now add friction. Under what condition will the box not
accelerate?
Run
Applet... (After running the Applet, use your browser's "back"
button to return to
this page.)
This next applets also has a box on an inclined plane but now attached
to another hanging mass via a sting and a pulley. The sting and pulley
are assumed to be massless and frictionless. Once again start with zero
friction and play with the masses and angle of the plane to see that
the masses can be made to accelerate in either direction. Calculate the
acceleration you expect and see that the applet predicts the same
result. Then add some friction.
Run Applet...
(After running the Applet, use your browser's "back" button to return
to
this page.)
This last Applet shows another example where friction forces are
present.
Mass m_{3} = 10 kg hangs by a massless string which
goes over a massless and frictionless pulley and is attached to a mass
m_{2}
= 10 kg upon which another mass m_{1} = 10 kg sits. You
can set the coefficient of friction, which is the same between the mass
m_{2}
and the surface and between the two masses. In this simulation the
coefficient
of static friction is equal to the coefficient of kinetic friction.
Then
run the simulation and see what happens. (Note: When setting the
coefficient
of friction, be sure to hit "enter" after entering the number to make
the
new value take effect.)
Do the following:
 Set the coefficient of friction to 0.2. See that the two masses
remain
together. Calculate the acceleration of the two masses for this case. [
Answer: 1.96 m/s^{2}]
 Set the coefficient of friction to 0.1. See what happens to the
two masses
now. Calculate the acceleration of the mass m_{2}
while the mass m_{3} is still on top of it. [Answer:
3.43
m/s^{2}] Then calculate the acceleration of the mass m_{2}
after the mass m_{3} has fallen off it. [Answer: 4.41
m/s^{2}]
 Note the vector diagram at the left of the simulation. It shows
the vector
sum of all the forces on the mass m_{2}.
[Hint: When doing the calculations, note that the three masses
are
the same (call it m). You don't even need to know that m
= 10 kg.]
Run
Applet... (After running the Applet, use your browser's "back"
button to return to
this page.)
Applets 7  Newton's
Mountain Cannon
This Applet shows the path of a cannonball fired from the top of a tall
mountain. Instructions for using the Applet appear with the applet
itself.
Run Applet... (After
running the Applet, use your browser's "back" button to return to
this page.)
Applets 8  Force and
Work
This applet shows you the total work that you do on a box as
you
move it around. You can move it sideways and vertically. When you slide
it on the surface you can choose whether there is friction present or
not.
Run
Applet... (After running the Applet, use your browser's "back"
button to return to
this page.)
This applet show the scaler product or dot product. Drag the head of
the vector arrow the change its magnitude and direction. Drag the line
part of the vectors to change only its angle and keep the magnitude
constant. The magnitude of the resulting dot product is displayed by
the bar at the right.
Run
Applet... (After running the Applet, use your browser's "back"
button to return to
this page.)
Applets 9  Integration
and the area under a curve.
This applet shows the area under a curve. As you drag the red dot on
the left graph to the right you will see the area under the curve
plotted on the right graph. That graph represent the integral under the
curve shown on the left graph. Once you have done that you can see that
the slope of the curve on the right is given by the curve on the left.
Thus you can see that integration is the inverse operation to
differentiation.
Run Applet...
(After running the Applet, use your browser's "back" button to return
to
this page.)
Applets 10 
Conservation
of Energy for a Pendulum
This Applet shows a pendulum swinging back and forth. Under the
pendulum
is shown a continuous plot of the Kinetic Energy (labeled K and shown
in
red) of the pendulum bob and the Gravitational Potential Energy
(labeled
U and shown in blue) of the bob. The simulation assumes no energy is
lost
to friction as the bob swings back and forth. If you click on the gray
area you can change the initial position of the bob. By clicking near
the
red dot you can change the length of the pendulum.
Things to note:
 The total mechanical energy is at all times constant. Why?
 What force other than gravity acts on the bob as it swings? Why
doesn't
this force matter when considering conservation of energy?
 Note that the red vector shows the instantaneous velocity of the
bob at
all times. If you click on the "show" check box you will see a blue
vector
which is the force of gravity vector. the green vectors are the
components
of the force of gravity along the line of the string and perpendicular
to the string.
Run
Applet... (After running the Applet, use your browser's "back"
button
to return to this page.)
Applets 11  Collisions
This first Applet show the collision between two bodies in 1dimension.
This is similar to the simulation of the collision between two cars we
showed in class. You can change:
 The velocities of each body.
 The mass of each body.
 The elasticity of the collision  100% elastic means an elastic
collision.
0% elastic means the two bodies stick together after the collision,
which
is a perfectly inelastic collision.
Try changing all the parameters and observe how the collision looks
different
in each case. Notice how momentum is always conserved, but the total
kinetic
energy is only conserved when there is an elastic collision.
Run
Applet...(After running the Applet, use your browser's "back"
button
to return to this page.)
This second Applet shows the elastic collision between two balls and
illustrates the Conservation of Momentum and Conservation of Kinetic
Energy. Suggestions for using the Applet appear with the applet itself.
Run Applet...(After
running the Applet, use your browser's "back" button
to return to this page.)
Applets 12  Motion of
the Centre of Mass
This applet show the motion of the centre of mass of a complicated
object that is rotating. Click "start" to start the applet. You can
then run it with different initial velocity, angular speed and mass
ratio that make up the object. Note that the centre of mass follows the
same parabolic path in each case (air resistance is ignored).
Run
Applet... (After running the Applet, use your browser's "back"
button
to return to this page.)
Applets 13  Rolling
motion
This Applet shows a wheel rolling without slipping. There are many
things
displayed in this applet and it can be confusing so we will concentrate
on only one thing at a time.
 First, look at the rolling wheel at the bottom of the screen. The
white
vector represents the velocity of the centre of the wheel. The red
vector is the velocity of a point on the rim of the wheel relative
to
the centre of the wheel. Notice that it is always at a tangent to
the
rim of the wheel and at right angles to the radius, denoted by the
yellow
arrow. The gray vector is the sum of the red vector and the white
vector
and is the total velocity of a point on the rim of the wheel relative
to the ground. Notice that this velocity (the gray vector) is not
constant, it is constantly changing. Note that at the top of the
wheel
this velocity has greatest magnitude, equal to twice the velocity of
the
wheel. At the bottom of the wheel this total velocity is
instantaneously
zero. At other points on the wheel it has a different velocity. The
green
line at the bottom show the complicated motion of a point on the rim of
a rolling wheel.
 The three circles at the top are representations of simple
circular motion
at a constant speed. The left hand one shows the actual circular
motion.
The yellow line is the radius and the red
vector is the velocity a point going in a circle at a constant speed.
The
green line shows the path of the point. The centre circle shows what
the
velocity vector is doing as time goes on. If we imaging the tail of the
velocity vector fixed at one point we see that the velocity vector is
also
going around in a circle. Notice that it is always pointing in the same
direction at the velocity vector in the left circle. The blue
vector acceleration of the point. The change in velocity in a small
time
interval is always perpendicular to the velocity vector. So if we show
the acceleration vector on the point going in a circle, as is done in
the
right hand circle, we see that it always points toward the centre of
the
circle. This is the centripetal acceleration.
Run
Applet... (After running the Applet, use your browser's "back"
button
to return to this page.)
This simpler applet than the one above shows some of the same things in
a slightly easier to view manner.
Run
Applet... (After running the Applet, use your browser's "back"
button
to return to this page.)
Applets 14  The
Vector or Cross Product
This applet give a three dimensional representation of the Cross
Product of two vectors A and B. You can change the components of either
vector and see the resulting Cross product. You will need to adjust one
of the sliders to initially bring the applet to life.
Run
Applet... (After running the Applet, use your browser's "back"
button
to return to this page.)
Applets 15  Motion
under different kinds of force
This applet show the motion of a particle under many different types of
forces. E.g. a constant force (as in projectile motion) and a force
always perpendicular to velocity (circular motion). But I introduce it
here specifically to show the motion under a central force that is
proportional to 1/r^{2}, which is the type of motion seen under
gravity.
The instructions on how to set up the applet and get it started are
under the applet itself. Play around with the different types of
forces. Note particularly that the 1/r^{2} central force gives
a closed orbit that is an ellipse.
Run Applet... (After running the Applet, use your browser's "back"
button
to return to this page.)
Applets 16  Kepler's
Laws
Kepler's First Law  Planets move in ellipses
Run Applet... (After running the Applet, use your browser's "back"
button
to return to this page.)
Kepler's Second Law  Planets sweep out equal areas in equal
times.
Run Applet... (After running the Applet, use your browser's "back"
button
to return to this page.)
Applet 17  The
buoyant force
This applet show the change in apparent weight of an object, as
measured by a spring gauge, as it is immersed in a fluid.
Run Applet... (After running the Applet, use your browser's "back"
button
to return to this page.)
Applet 18  SHM and
Circular Motion
This Applet shows the relationship between uniform circular motion and
Simple Harmonic Motion (SHM). The masses on the springs at the bottom
and
the side oscillate in SHM. The thumbtack on the table rotates with the
same period. You can see the relationship between the projection of the
circular motion and the oscillating masses. The red vector on the blue
mass indicates its velocity. Notice that it is always the same as the
blue
vector on the rotating thumbtack, which is the projection on the yaxis
of the red vector on the thumbtack which is the velocity of the
thumbtack.
i.e. the ycomponent of the velocity. You can pause the motion at any
time
by clicking and holding down the left mouse button in any part of the
gray
box. Notice also that the graph of the position of the blue mass, and
the
y position of the thumbtack, as a function of time looks like a sine
function,
a signature of SHM.
Run Applet... (After running the Applet, use your browser's "back"
button
to return to this page.)
This second applet shows much the same thing.
Run
Applet... (After running the Applet, use your browser's "back"
button
to return to this page.)
Applet 19  Simple
Pendulum
Look again at the applet for the simple pendulum. You can change the
length
of the pendulum, its mass and the acceleration due to gravity. The
resulting
period of the pendulum is shown in the upper left hand corner. Notice
how
it varies as you change the above quantities. Notice too what happens
to
the period when you make the amplitude of the pendulum's swing very
large.
The approximation of small angle swings is not valid then.
Run
Applet... (After running the Applet, use your browser's "back"
button
to return to this page.)
Applet 20  Damped
Oscillations
This applet shows simple harmonic oscillations with a damping factor
for
the case where the damping force is proportional to the speed.
Initially the damping factor, b, is zero. Slowly increase b
to find the point where oscillations cease.
Run
Applet... (After running the Applet, use your browser's "back"
button
to return to this page.)
Applet 21  Forced
Oscillations
Initially the end of the spring is wiggled at a frequency that is not
equal to the natural frequency of the mass and spring system. notice
that the amplitude of the resulting oscillations are not very large.
Increase the driving frequency (the exciter angular frequency in the
applet) and note what happens. When the driving frequency is close to
the natural frequency of the system the amplitude of the vibrations can
rapidly become large.
Run
Applet... (After running the Applet, use your browser's "back"
button
to return to this page.)
A dramatic example of forced oscillations  The
Tacoma Narrows Bridge  collapsed 1940. (avi movie).
Applets 22 
Transverse and Longitudinal Waves
A graphic illustration of the two basic types of waves  Transverse and
Longitudinal. You can change the wavelength of the waves by changing
the wave number k (the wavelength is proportional to 1/k so a larger k
gives
a shorter wavelength) and you can also change the frequency of the
waves. The "mixture" picture shows what a combination
Transverse and Longitudinal wave would look like. Water waves on the
ocean
are actually waves of this type.
Run
Applet... (After running the Applet, use your browser's "back"
button
to return to this page.)
Here are two more applets that demonstrate Transverse waves (Run
Applet...) and Longitudinal waves (Run
Applet...)
And two more demonstrating Transverse waves (Run
Applet...) and Longitudinal waves (Run
Applet...)
Applets 23  The
Reflection and Transmission of Waves
This applet show the reflection of a wave pulse from a fixed end and
from a free end. It can also show what happens when a wave pulse is
incident on a join in two ropes that have different thicknesses, and
therefore different speeds of propagation.
Run
Applet... (After running the Applet, use your browser's "back"
button
to return to this page.)
This applet shows the reflection of a wave pulse or a periodic wave
from
either a fixed end or a free end.
Run
Applet... (After running the Applet, use your browser's "back"
button
to return to this page.)
Applets 24  The
Doppler Effect
This applet show a moving source of sound (the red dot). It also shows
the wave fronts moving out from the place where they were emitted. You
can change the speed of sound and the speed of the source (in relative
units).
 Make the speed of the source less that the speed of sound and
note the
bunching up of the wave front in front of the source, and the spreading
out of the wave fronts behind the source. Play with different values.
you
can also change the period of sound souse (1/frequency).
 When the speed of the sound source is greater than the speed of
sound you
are "breaking the sound barrier". Notice the shock wave fronts heading
out from the source in a V formation. This is what happens when a plane
travels faster than the speed of sound. The shock wave is the "sonic
boom".
Run
Applet...(After
running the Applet, use your browser's "back" button to return to this
page.)
Another Doppler Effect applet:
Run
Applet...(After running the Applet, use your browser's "back"
button
to return to this page.)
Sound files:
Applets 25  The
Superposition of Waves
The first applet show the superposition of two wave pulses. One from
the
left and one from the right. Notice what happens when they overlap each
other. You can flip a pulse upside down by clicking under it. Click and
hold the right mouse button to pause the simulation.
Run
Applet...
(After running the Applet, use your browser's "back" button to return
to
this page.)
Another applet showing the superposition of two wave pulses. You can
step through the animation frame by frame. Choose Phase: Out to see the
animation with one pulse upside down.
Run
Applet... (After running the Applet, use your browser's "back"
button
to return to this page.)
This applet shows the same thing as the above applet, except with
longitudinal
waves.
Run
Applet... (After running the Applet, use your browser's "back"
button
to return to this page.)
This applet show the two dimensional interference of water waves
from two coherent sources. This is rather like the interference of
sound
waves from two speakers that are in phase. You can see how the
different path difference results in constructive or destructive
interference at different points.
Run
Applet... (After running the Applet, use your browser's "back"
button
to return to this page.)
Applets 26  Standing
waves
This applet can show the standing wave pattern such as will exist in
guitar
string (both ends fixed). It can also shows the pattern of a sound wave
in an organ pipe (one end free or both ends free). Do the following:
With both ends fixed (it is probably easiest to see if you
don't check "components" and "particles".)
 Observe the pattern for each component separately each set to
100% and
the other 3 set to 0%.
 Put in extra components with the fundamental and see how
complicated the
pattern can become. This is what would occur in a real guitar string.
You
can use the applet in Applets 28 to hear what a complex pattern like
this
would sound like. Check "components" to see the individual overtones
that
add to give the observed pattern.
 Note: In this case:
 first overtone = 2nd harmonic
 second overtone = 3rd harmonic
 third overtone = 4th harmonic
With one end fixed.
 Repeat the exercises you did for both ends fixed.
 Note: In this case:
 first overtone = 3rd harmonic
 second overtone = 5rd harmonic
 third overtone = 7th harmonic
With both ends free.
 This simulation does not show the correct thing in this case.
It just shows a traveling wave, not a standing wave.
Run
Applet... (After running the Applet, use your browser's "back"
button
to return to this page.)
Applets 27  Resonance
This applet show what happens to a string, which is fixed at both ends,
when it is wiggled at a given frequency. Change the frequency and you
will find those frequencies that give large amplitude standing waves.
These are the resonance frequencies which are equal to the harmonic
frequencies of the string fixed at both end.
Run
Applet... (After running the Applet, use your browser's "back"
button
to return to this page.)
Applets 28  Beats
This applet shows the phenomenon of Beats. Change the frequencies
of the two waves and see how the sum changes. Read the notes below the
applet for more information.
Run
Applet... (After running the Applet, use your browser's "back"
button
to return to this page.)
This Applet shows the result as a function of time at a fixed point
in space.
 W1 and W1 are the angular frequencies of the two waves.
 A0_1 and A0_2 are the amplitudes of the two waves.
 Phi_1 and Phi_2 are the phases of the two waves (in radians).
Don't worry
too much about these, we don't discuss phases much in this course. You
can make the waves 180 degrees out of phase by putting Phi_1 = 0 and
Phi_2
= 3.14 (pi). Try it when W1 = W1 and A0_1 = A0_2.
 Try making W1 = W2 = 0.20, with A0_1 = A0_2 = 30 and Phi_1 =
Phi_2 = 0.
Observe the pattern then change W2 = 0.22 and see the change. This is
the
Beats phenomenon.
Run
Applet... (After running the Applet, use your browser's "back"
button
to return to this page.)
Applets 29  The
Sound of Complex Waveforms
This applet will allow you to see and hear a complex waveform. You
can
change the amounts of each harmonic and see the shape of the waveform
as
a function of time. By pressing the "play" button you can also hear the
resulting sound. Checking the box in the top righthand corner also
show
the intensity of the wave (the square of the wave amplitude) in yellow.
The green sliders (labeled "cos") add waves that are 90° out
of
phase with the blue slider waves (labeled "sin").
(It is probably a good idea to click "stop" before leaving the page
 I have found that my computer's sound card sometimes gets "stuck" on
otherwise.)
Different musical instruments have different sounds because they
have
different amounts of the various harmonics even though they may be
playing
the same fundamental frequency.
Run
Applet...
(After running the Applet, use your browser's "back" button to return
to
this page.)
Applets 30 
Electromagnetic Wave
This Java applet simply shows you what an electromagnetic wave might
look
like from an antenna. You can see how the electric and magnetic field
vectors
oscillate.
Run
Applet...
(After running the Applet, use your browser's "back" button to return
to
this page.)
Applets 31 
Reflection and Refraction
This Java applet shows you rays and waves reflecting and refracting off
an interface between two materials. You can change which materials are
displayed from a drop down list or you can put in your own ratio of the
refractive indexes. You can also change the angle of incidence by
dragging
the black dot at the top.
Things to note:
 See how the angle of reflection and refraction are form by the
waves
radiating
out from the interface.
 Note the different speeds of the waves in the different materials.
 See that total internal reflection occurs when the conditions are
right.
What conditions are these?
The simulation will also show sound waves as well as light.
Run
Applet... (After running the Applet, use your browser's "back"
button
to return to this page.)
This applet shows how rays of light are reflected and refracted by a
water droplet forming the dispersion that results in a rainbow.
Run
Applet... (After running the Applet, use your browser's "back"
button
to return to this page.)
Applets 32  Mirrors
and Lenses
This Java applet allows you to play with Mirrors and Lenses, both
concave and convex mirror and converging
and diverging lenses. You can move the mirror or lens around (by
dragging it) and you can
move the object and change its size (by dragging the object arrow
head).
The object distance is labeled p and the image distance is labeled q in
this simulation. Clicking on the + or  box you can change the mirror
from concave to convex or change the lens from being converging to
diverging. You can also change
the focal length f.
 The main thing is to play with all the combinations. Note where
the
image
is relative to the focal points of the lens. The distance of 2f is also
shown.
 Note in each situation whether the image is real or virtual,
upright or
inverted, reduced or enlarged. The calculated magnification m is also
displayed.
 The principal rays are also drawn. Note how to find the image
yourself
using the principal rays. (You won't have this applet in an exam!)
 The default is to show paraxial rays. By unchecking this box you
can see the spherical abberation effects.
Run
Applet...
(After running the Applet, use your browser's "back" button to return
to
this page. You will need to close the applet window as well.)
Also check out this applet which shows rays of light passing through a
thick lens. You can change the thickness of the the lens and see how
rays of light parallel to the principal axis are affected. Notice that
if you change the distance of the light rays from the principal axis
the focal point changes (this is spherical abberation), but if the rays
of light are restricted to being close to the principal axis the focal
point is approximately at the same position.
Run
Applet... (After running the Applet, use your browser's "back"
button to return to
this page.)
Applets 33  Thin Lens
Combinations
This Java applet allows you to see a wider range of effects than
you can with the previous applet. You can see the effect of a
twodimensional
object rather than a one dimensional one. Also you can see the effect
of
having two lenses instead of one.
The object is a box with four coloured dots at the corners and white
lines.
 Clicking on the green
dot will change which corner's rays are displayed.
 Dragging the red
dot will move the box around.
 Dragging the blue
dot will change the size and shape of the box.
 Dragging anywhere in the lens will move
the
lens.
 Dragging the hollow gray circle will change
the focal
length of the lens.
 The object distance for the displayed
coloured corner
is labeled p and the image distance is labeled q.
 Clicking with the right mouse button will
introduce
a second lens (clicking again will remove it).
 The second lens's position and focal length
can be
changed in the same manner as the first lens.
 The intermediate image (through the first
lens, ignoring
the second lens) is shown with hollow coloured circles at the corners
and
gray lines.
Run
Applet...
(After running the Applet, use your browser's "back" button to return
to
this page.)
Applets 34 
Accommodation
This simple Shockwave Applet show the accommodation effect of the eye.
As the distance of the object changes the focal length of the eye must
change since the image distance is fixed.
Run
Applet...
(After running the Applet, use your browser's "back" button to return
to
this page.)
Applets 35  Young's
Double Slit Interference
This applet show the interference of light (Young's double slit
experiment)
for various wavelengths, slit separations and distances to a screen.
Run Applet...
(After running the Applet, use your browser's "back" button to return
to
this page.)
The following applet show what happens as you add extra slits (or
sources) to the two slits. Many slits becomes a Diffraction grating.
Run
Applet... (After running the Applet, use your browser's "back"
button to return to
this page.)
Finally a look at one of the weird quantum effects associated with the
double slit experiment. It works, not only with light (which is
actually quantized particles known as photons, as well as behaving like
a wave), but also with real particles such as electrons. It is a video
clip from the movie "What the Bleep do We Know?"
Play
Movie...
Applets 36  Single
Slit Diffraction
This applet show the diffraction patter obtained from a single slit on
a screen. When the applet start you see the experiment. Adjust the
slittoscreen distance, the slit width, and the wavelength of the
light to see the effect on the diffraction pattern.
Then choose results from the menu to see a plot of the intensity
distribution you see on the screen. If you move you mouse up into the
graph part of the screen, and move it from side to side, you will see
how the phaser addition of several dozen phasors from different part of
the slit add to give the final amplitude of the wave at each place on
the screen.
Run
Applet...
(After running the Applet, use your browser's "back" button to return
to
this page.)
Applets 37 
Thinfilm Interference and Diffraction Patterns
This applet shows the thinfilm interference effect as applied to the
lens coating situation.
Run Applet...
(After running the Applet, use your browser's "back" button to return
to
this page.)
This applet allows you to create you own hole pattern in a slide, and
then see the diffraction pattern you would get. Read the instructions
with the applet to see how to use it.
Run
Applet...
(After running the Applet, use your browser's "back" button to return
to
this page.)
Applets 38 
Electric Field Lines and Equipotential Surfaces
This applet shows the electric field lines around one or two charges.
You
can change the sign of the charges. With two charges you can change the
sign and magnitude of one of the charges. You can also choose to
display
the equipotential surfaces.
Note:
 When the charge is larger you have larger electric fields.
 When the electric field lines are closer together the magnitude
of the
field is largest.
 When you have two opposite charges you have a dipole.
 The equipotential surfaces are always perpendicular to the
electric field
lines.
Run
Applet... (After running the Applet, use your browser's "back"
button
to return to this page.)
Another applet that shows in more detail all manner of electrostatic
quantities. Select "Setup: single charge" or "Setup: Dipole Charge" or
"Setup: Double Charge" to show the same things as the previous applet.
Select "Show E lines". You can select many other charge distributions
as well.
Run Applet... (After
running the Applet, use your browser's "back" button
to return to this page.)
This next applet is part of the Physics 2000 website. Scroll down to
find the applet which is a rectangle with a positive and negative
charge
in it. Click anywhere in the rectangle to see the force on a test
positive charge
if it is placed at that point (Note: the text near the applets
says you are placing electrons. This is not correct The force
on an electron would be toward the positive charge not away from it).
Place several and see that the force is
strongest nearest to the charges. Note the direction of the forces.
Place
many test charges and see the pattern created. Press 'R' to place many
at one time. You will
build up a picture of the electric field lines. Press 'L' and you will
see the
electric field lines.
Run
Applet... (After running the Applet, use your browser's "back"
button
to return to this page.)
Applets 39 
Electric Circuits
This Shockwave applet allows you to make up your own electric circuits
and see current flow and measure the voltage and current in different
parts
of the circuit. Follow the instructions with the applet.
Note:
 The wires do have a finite but small resistance.
 Use Controlleft click to switch a switch.
Run Applet...
(After
running the Applet, use your browser's "back" button to return to this
page.)
Applets 40 
Magnetic Fields
This applet shows the magnetic field around a bar magnet. Move the
compass needle around to find the magnetic field at each place.
Run Applet...
(After
running the Applet, use your browser's "back" button to return to this
page.)
This applet shows the magnetic field around a current carrying wire.
Again move the compass needle around.
Run Applet...
(After
running the Applet, use your browser's "back" button to return to this
page.)
Applets 41 
Lorentz Force
This applet shows the path of a charged particle in a magnetic field.
You can change the charge and velocity of the particle and the magnetic
field.
Run
Applet...
(After
running the Applet, use your browser's "back" button to return to this
page.)
Another applet showing the force on a charged particle moving in a
magnetic field.
Run
Applet...
(After
running the Applet, use your browser's "back" button to return to this
page.)
This applet shows the Lorentz (or Magnetic) Force on a current carrying
wire.
Run
Applet...
(After
running the Applet, use your browser's "back" button to return to this
page.)
Applets 42  Motors
and Generators
This applet illustrates the principle of a simple direct current
electric motor.
Run
Applet...
(After
running the Applet, use your browser's "back" button to return to this
page.)
This applet illustrates the principle of an electric generator. You can
change it from an AC generator to a DC generator.
Run Applet...
(After
running the Applet, use your browser's "back" button to return to this
page.)