CoolStuff Newsletters

Demonstration of The Photoelectric Effect!


In 1905 Albert Einstein had his miracle year, publishing 5 papers, including the Special Theory of Relativity, the Mathematical Description of Brownian Motion, and the E=mc2 formula.  One of these papers was titled “On a Heuristic Point of View about the Creation and Conversion of Light.” [Ref 1]  In section 8 of this paper he develops a mathematic model that describes how light creates cathode rays.  What was heuristic was that he described light as “energy quanta” (photons) for the first time but what was worth a Nobel Prize, was that he was correct.

Figure 1.A –Max Planck presents Einstein with the 1929 Planck Medal for extraordinary achievements in theoretical physics.

Figure 1. B – Albert Einstein c1905 at the patent office desk where he worked as a third-class clerk, and occasionally worked on his “miracle” papers.

It is quite easy to demonstrate the photoelectric effect with an electroscope and a short wave UV-C lamp. By placing a negative charge on the electroscope, and shining the short wave UV light on top, it will discharge. Short wave UV is usually blocked by glass, but visible light is not, thus a pane of glass can be used to show that it is not just regular light that is causing the discharge.

Figure 2 – The electroscope is discharged by shining short wave ultraviolet light upon it.

It helps that on the top of the electroscope there is a zinc plate which has been scrubbed with steel wool.  This removes the zinc oxide layer and makes it more sensitive to the light.  Also note that if the experiment is tried with a positive charge, for example with a piece of glass rubbed with silk, it will fail to discharge.  This is because the photoelectric effect is only for electrons and will only work on negative charges because they are at the surface, but the positive charges are held deep in the nucleus by the strong force. In fact, the photoelectric effect is a great way to identify positive vs. negative charge.

With any form of visible light, you will not get the electroscope to discharge. It does not matter how bright the light is, even lasers will fail.  It takes ultraviolet, specifically the short wave UV-C, because even blacklights are not energetic enough to liberate the electrons.

The thing with light is, the shorter wavelength the more energy it has, and this was already well-known, from Max Planck’s formula  E = h f  but what was worth a Nobel prize, was the idea that the light hits one electron at a time.  Not as waves, but as individual pieces of light.  ONE particle of light hitting ONE electron at a time.  Einstein called this particle a quantum of light, meaning that it is a discrete exchange of energy.  We now call this a PHOTON.

Figure 3 – Albert Einstein took Max Planck’s formula for the quantization of energy in black bodies and extended it to describe light.  This implied that light delivered its energy in bundles of E=hf.  This was a new and heuristic idea, but it explained the photoelectric effect.  KE is the energy of the escaping electrons and W is the energy required to liberate them from the metal.

Figure 4 – The Phet Simulation of the photoelectric effect is a great way to engage students with the details of this modern physics concept. It is based on the experiments of Robert A. Millikan who proved Einstein’s perspective by experiment.

It is also possible to demonstrate the photoelectric effect with a small neon bulb.  These will turn on at about 70 volts.  Hook one to a high voltage source and then dial it back until it is just about to turn on.  Now it will be so sensitive, that just a little extra energy will make the electrons jump and conduct. This will NOT work for red and green light.  It must be blue, or ultraviolet.  That’s right, blue light ACTUALLY DOES have more energy than red and green light.  This is because light travels as photons, and the shorter the wavelength of light, the more energy per photon.

Figure 5 – The energy of blue light can cause electron conduction in a small neon bulb. The bulb stays on because plasma conducts better than rarefied neon.


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Reflection, Refraction, Diffraction & Interference…… That’s COOL!

The Mini Ripple Tank is a great way to address the wave-energy standards and to teach about the properties of waves by showing how water waves behave.  This is in keeping with the history of physics and the modern experimental approaches to science instruction.

The Mini Ripple Tank eliminates the clumsiness of the larger ripple tanks of old and gives the opportunity for students and teachers to interact with the wave properties quickly and engagingly.  Because of the competitive price, and variety of available experiments.  It is even reasonable to buy a class set.

Fig 1.  Plane waves are being produced and are readily visible on the built-in screen.

Getting Familiar

The Mini Ripple Tank contains a small pan for water and a vibrating source.  The strobe light below projects waves of various frequencies on a fold-down screen.  Both the strobe and the wave frequencies can be varied, generating many interesting effects.  There is also a synchronizing mode which links the two (this is very helpful when measuring wavelength).

Fig 2. Water is filled up to half of the height.  The adjustable strobe projects from underneath.

The device comes with three distinct wave generating mechanisms: single source, double source, and plane waves.  The single source is the most fundamental and is helpful in instructing on wave basics and Huy gen’s Principle (plane waves are a sum of circular waves).  The double source can be used best at teaching interference experiments (more below) as well as testing out the diffraction formula.  The plane wave source is the one I tend to use the most often because it sets up a standard wave that can readily land upon the other implements which are used to redirect the waves.

Fig 3. The nine components.  Left to right: the two lenses and the prism, the two barriers and the parabolic mirror, and the double and single sources, as well as the plane wave source.

As for general tips, it is helpful to use a document camera for larger classes, also adding blue dye can sometimes improve visibility, and try to not overload the tank with water – either fill halfway or just enough to barely cover the lenses and prism.  Experiment a lot with wave and strobe speeds to improve the visibility of the desired effects.  

Refraction by the Lenses and the Prism

The bending of light waves by glass is well-known, but is this a property of all waves?  Yes! Demonstrate this dramatically by bending water waves with lenses and prisms.  The shallower the water, the slower the waves.  This is analogous to the denser the medium, the slower the light waves (with few exceptions).  

Fig 4. The prism can bend the waves by slowing their propagation.  

Again, remember to keep the water shallow.  Some experiments can include measuring the focal lengths of the two lenses (positive for convex, negative for concave), measuring the index of refraction for the prism (by wavelength change, speed change, or Snell’s Law), and measuring how water depth affects refractive index.  

Fig 5. The refraction formulas that can be used for quantitative experiments.  The first formula might be the least familiar – wavelength changes with index of refraction.  The second formula compares a standard speed c with the new slower one v to define the index n.  The third is the famous Snell’s Law.  

Somehow it is very satisfying to see the focusing of water waves when using lenses.  The ray approach to drawing images known as geometric optics does not provide a hypothesis as to the wave nature of light, but this experiment convincingly demonstrates that refraction and focusing is something that waves do!  Refraction and lens effects are a powerful piece of evidence that demonstrates the wave nature of light.  

Fig 6. The convex and concave lenses demonstrate convergence and divergence of waves respectively.

Reflection by Barriers and the Parabolic Mirror

The law of reflection can be readily demonstrated by the Mini Ripple Tanks (by stacking the barrier pieces) however, the best demonstration is the focusing of waves by the parabolic mirror.

When a plane wave enters parallel to the axis of a parabolic mirror, it will be reflected to the focus of that mirror.  This is the basis for Newtonian Reflector telescopes that remain the standard style in modern times.  A reversal can also be achieved by placing the single source at the focal point and reflecting out plane waves.  

Fig 7.  Reflection of plane waves off a parabolic mirror will focus them to a point.  

Diffraction by Barriers

le-slit diffraction of waves is easily demonstrated with this simple device.  Just place the barriers in the path of the plane wave source and the effect is immediately present.  Manipulating the opening and wavelength can help illustrate the variables: more diffraction occurs the smaller the opening is allowed to be.

Fig 8.  Single slit diffraction shows the bending of a plane wave source as it passes through an opening, illustrating Huygen’s Principle that plane waves are a sum of circular waves.

The diffraction formula for quantitative experiments is best applied to the two-source case, however, and while this is only a case of interference and not diffraction, it does provide an opportunity to apply the formula experimentally.    Here, we see both versions of the formula, the angular version, and the small angle approximation.  I prefer the second one because lengths are usually easier to measure than angles.    

Fig 9. The diffraction formulas:  The symbol d represents the distance between the sources, and lambda as always is wavelength (which is the dependent variable in this experiment).  Theta is the angular distance to an interference fringe as measured from the spot half-way between the sources.  X is the linear distance between the interference fringes, these are the locations of constructive interference.  L is the linear distance from the point between the sources to the point of interest, and because there is more than one location of constructive interference, m is the index number which labels these points as m=1,0,-1,2, etc, (any integer).  

Fig 10. An interference pattern is easily generated with these two sources.  The diffraction formulas above will apply to this double source interference pattern, even though no diffraction is occurring.  This demonstration can be converted into a quantitative experiment.


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Powering Imagination and Creativity OneCar at a Time

The OneCar is Arbor Scientific’s answer to the various needs of STEM Educators.


OneCar is an open-ended creativity-driven approach to science teaching that addresses cross-cutting concepts and offers an opportunity for tinkering and design.
Pictured here is one of the eight OneCar Packets which comes in every kit. Each can be used to construct eight different cars. Students can be creative.

Pictured here is one of the eight OneCar Packets which comes in every kit. Each can be used to construct eight different cars. Students can be creative.

 The kit itself is jam-packed with 8 sets of experiment options, enough for large classes and extras for spare parts.

A typical starter lab would be building the battery powered motor car.

A motor in its housing slides into the chassis. These cars can be assembled and disassembled each class period.

This might be used for speed and acceleration experiments. But the options expand rapidly as more options are introduced.

The OneCar offers 8 ready to go experiment options. These can be extended and combined in creative ways to allow for the open-ended labs that STEM teachers have been searching for.

For example, the motor can be used to drive a fan, or be powered by a rechargeable capacitor. The lessons can go beyond physics or include chemistry lessons such as air pressure and electro chemistry or even acid-base reactions. Perfect for Physical Sciences courses. There is more too. The Potential energy in a rubber band lab or the classic mousetrap car can be readily created using this kit.

The rubber band-powered car can be used to investigate potential energy.

The mousetrap car is a classic lab in physics used to teach energy and simple machines. Adding a lever arm and CDs for wheels is a common innovation.

You can also build a solar powered car. Challenge your students to discover what can be done to optimize its traveling speed? Face it south? Angle the collar panel? Use a mirror to reflect the sunlight?

A solar powered car can be created and manipulated to optimize its efficiency. The solar panel can be either connected directly to the motor or, in this case, used to charge up one of the super-capacitors. Note how the solar panel is angled to be perpendicular to the sun, just like solar panels on rooftops.

 All of these options can be mixed and matched. That is the whole idea of open-ended inquiry education. The OneCar gives students many opportunities to be creative in solving engineering challenges. Many of the above images come from videos on our website: .   Take a look at the website and see how fun and easy it is to build these designs.



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Lab4Physics Classroom Edition Powered by Arbor Scientific

The Lab4Physics App is a helpful tool for teaching physics and physical science. It is a lab app for smartphones and tablets, and because of the familiar controls and friendly, easy-to-use interface, all your students can use it


The App works by using the built-in features of cell phones and tablets that convert easily to probeware, such as the accelerometer, which we will explore first.

Fig 1.  The Lab4Physics home screen.  When you open the app, there are lots of experiments you can try (which are categorized on the left) or you can go straight to the tools (right) and perform your own experiments.




If you shake the phone up and down, the accelerometer records this motion in 3D. Deleting the X and Z axis, we will now graph only the Y-vertical motion.

Fig 2.  It is easy to use the accelerometer to measure the earth’s gravity field strength.  Here the phone was held vertical then slowly turned to lay flat.  The gravity constant 9.8 m/s2 is measured.

The app allows you to zoom in, both vertically and horizontally, and slide the image around, just like a picture or map.  Because this interface is so familiar, students will already know how to do this.

Fig 3.  The phone’s Acceleration is measured in 3 dimensions, but typically you only need one.

Because the accelerometer is so easy to use, you will find yourself using it in many different applications, such as spring and pendulum experiments.  Note that when facing the phone, X is right and left, Y is up and down, and Z is toward and away.  The positive axes are right, up, and toward, which you can remember with thumb X, open fingers Y, palm-slap Z.

Fig 4.  Zoomed-in on the image of the above data.  Vertical zoom for precise amplitude measurements and horizontal zoom for precise time (period) measurements.

Fig 5.  A plastic bag is a convenient container for the phone when performing spring and pendulum experiments.  The touchscreen still works fine through the plastic.




Using the microphone, Lab4Physics can analyze the intensity and frequency of a sound that the phone records. With this device, you can see the waveform of the frequencies that the phone picked up. Use this to compare the amplitudes of loud and quiet sounds or the frequencies of a high and low pitch.  This works as an instant oscilloscope. It is also possible to measure the period as the time between peaks, it helps to zoom in for this.

Fig 6.  The Sonometer makes a measurement of the author’s whistling ability.  The period can be measured as the peak to peak time, or the Highest peak frequency can be displayed automatically by using the Intensity vs. Frequency feature.

The waveform displayed looks transverse, but the sound is a longitudinal wave.  Therefore, it is important to explain how this wave was generated.  It was the motion of the vibrating microphone that moved a small magnet that generated the electricity that became the signal displayed. The device also can calculate the frequency of the loudest part of the signal it is detecting.  This can be used to test who sings with the highest or lowest frequency or just to check the frequencies of musical instruments.

Fig 7.  A tuning fork, which is supposed to be the musical tuning standard A 440Hz, is revealed to be very nearly correct by the Lab4Physics App’s Sonometer feature.




One of the most useful features is the ability to track an object’s motion.  Utilizing the phone’s camera, film an object (usually with a ruler in the picture), and by tracking at a specific point on the object, you can follow its motion through the frames of footage.

Fig 8.  An accelerating toy car has its motion tracked through ten frames of footage generating the expected parabola of an accelerating object.

 Because the frames are equally separated by time intervals the app can turn this data into a distance vs. time graph.  From this data, it further generates the acceleration and velocity graphs.  Even a Data Table is provided so you can sort out anomalous data or analyze further.




Lab4Physics also has a speedometer which is a streamlined alternative to stopwatches.  Students can, for example, set up a series of positions and click the split button to get the individual times for when the object is at that position.  Using this, graphs are generated for position and velocity.

Fig 9. A typical Speedometer experiment. Tracking the position of a toy car through space. Changing it from going slow to fast can show up on a position vs. time graph.




Lab4Physics has lots of ready to go labs to instruct your students, or you can use them to give you ideas.  Here we explore some of the labs on waves.

Fig 10.  Left, a screenshot from the app shows the four labs on waves.  Choosing Do-Re-Mi takes us eventually to this screen, right, which shows how we will be exploring the frequency of a musical instrument.

 The labs take the students through the experiment in five or six steps.  They are self-contained and complete and let you know how much time the activity should take.


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Cool Stuff Demos with Violet Lasers


If you are talking about optics in the classroom and students are learning about how light waves behave, take a look at the blue-violet laser, which produces wavelengths at 405 nm.

“I definitely want one of those blue LASERS! Ahhhh… to write my name on a phosphorescent board the FIRST day of class in the dark from the back of the room. That WILL get their attention!”   -Buzz Putnam


Sure, it is a different color and that is always cool, but why use this over any other Laser?

  • Cover most of the visible spectrum – If you only have the red (650nm) and green (532nm) Lasers, you are still missing a large part of the visible spectrum. At 405nm, the blue-violet Laser provides a good representation of the shorter wavelengths present on the opposite end of the visible spectrum from red.
  • Diffraction grating differences – You can compare the red, green, and blue-violet Laser colors by pointing them through a diffraction grating to observe where the different wavelengths end up.
  • More Fluorescence – Unlike the green Laser, the blue-violet Laser can produce fluorescence on a wide variety of materials. In other words, the blue-violet wavelength of 405 nm excites the electrons of most materials to a higher energy level than the green Laser.
  • More phosphorescence – For your next trick, we recommend shining the Laser on something with “glow-in-the-dark” properties, such as a sheet of glow-in-the-dark paper. The effect, called phosphorescence, is due to the same characteristics of excited electrons that we saw in florescence. Only with phosphorescence, it takes longer for the material to transition back to its ground state, and therefore you see it longer with those types of materials. The green Laser does not produce these same effects. Show your students both situations and ask them why!


Why pay $79 for a violet LASER

Arbor Scientific has carefully screened all of our Lasers to make sure they offer a higher level of safety and peace of mind. There are low-cost versions available on the market today that could pose serious risk to your students due to a lack of infrared (IR) filters. Even pointers that use IR filtering could still be harmful, due to shoddy manufacturing that provides poor conversion efficiency (when converting from infra red to visible light). While all Lasers should be handled carefully to prevent users from harm and should never be pointed at unprotected eyeballs, these lower cost Lasers are particularly problematic in the academic atmosphere where there are many people in close proximity. For the safety of your students, please always make sure you have taken all the proper precautions possible, including the use of effective IR filtering.

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Air Powered Projectile in-depth look [W/Video]

The Air Powered Projectile in-depth look

One of the best ways to engage your students in the study of projectile motion is with direct experiment and observation. For this purpose I recommend the air-powered projectile. It safely and reliably demonstrates projectile motion by simply releasing compressed air. Here are five experiments to get you started.

The soft nose cone provides a high degree of safety while the body’s sleek design minimizes the effects of air resistance.

Shooting the projectile straight up is the easiest way to determine launch speed.
The first thing you want to do is determine the launch velocity by shooting straight up. It takes about 5 seconds to go up and come back down when shot vertically. Use the formula v=vo+at , analyze the top of the trajectory. At this point velocity = zero. Then set gravity to negative 10m/s/s. Gravity is pulling opposite the initial launch velocity, which is the unknown. Plugging in 2.5 seconds for time (assuming the trip takes the same time up as down) we get a launch velocity of about 25m/s. You might be concerned whether this is a safe speed, but the soft nose c one, and the fact that there is no chemical propellant ensures this. You may wish to wear safety goggles anyways.

The calculation of launch velocity is straight forward, requiring only algebra.

A classic experiment that I have done every year since I started teaching is to investigate which angle generates the greatest launch distance. Students will have their own hypothesis. Without doing any math, try to hypothesize which angle will maximize the range. This is an experiment that works in both high school and middle school. The theoretical result is that 45 degrees maximizes range.


Sample data for the Range vs Angle Experiment. Note the systematic error on the zero.
This is because the product of horizontal velocity and time in the air is maximized. The mathematical proof is a common homework problem in Honors Trigonometry classes and can be done without calculus. When you plot the data, a surprising result is that the complementary angles, like 30 and 60 degrees can have the same range as each other. This is because when the velocity is more horizontal, the vertical time is lessened, and vice versa.


Angled Wooden Wedges help a lot in this experiment. The angle of launch will be the compliment to these angles.
When performing this experiment, it is helpful to use the angled wooden wedges option. These help adjust the angle without the use of clumsy blocks of wood or coupling. Another addition you might want to invest in are the varied speed end caps. The different size caps affect the pressure limit that causes the seal to slip, launching the tube upward with the force of expanding gas. Larger endcaps can capture more of that force so it will go faster. This adds another variable which allows you to make new predictions. But with the same endcap, you get the same time, every time.


Different sized end caps can change the launch velocity, adding a new variable.
The air powered projectile does not use any chemicals to launch. It only uses the compressed air of a bike pump, typically around 60 psi (pounds/square inch). When you launch the projectile, you will usually see some clouds appearing beside the base. They only last for a second, but can be made more visible by using a high speed camera. (Many students now have these in their smartphones.)


Adiabatic clouds appearing during a typical launch event. This image was taken with an iPhone 5s in 120 frames/second mode.
The clouds are caused by the humidity in the air being turned into a vapor due to the rapid temperature change. When a gas expands rapidly, it cools. This is called adiabatic expansion. It is an important idea in thermodynamics and this is a really good example of it. You’ve probably seen it when you open a champagne bottle, or even a soda.

Because the force of launch only acts in the initial moment, the rocket is an excellent example of a free falling projectile (unlike missiles and rockets). The sleek profile minimizes air resistance and turbulence while increasing the accuracy of the experiment.

In video we launch the air powered projectile at 30 degrees, and from the first experiment, we already know the initial velocity, Vo=25m/s. We use Vo sin30 to find the initial upward velocity (12.5m/s) and Vo cos30 to find the horizontal component (21.6 m/s).


A typical projectile motion problem can now be performed experimentally, with a high degree of accuracy and while being highly engaging.
At the highest moment, it is only moving horizontally, so we once again can use v=vo+at. Only this time the plug step is 0=12.5-10t giving a time of 1.25 seconds to reach the top. Twice that is 2.5 seconds, the total time of flight.
The product of the horizontal component and the total time of flight is the distance traveled. (The horizontal velocity never changes.) The range, x=vhoriz * time = 21.6m/s * 2.5 sec = 54 m.
That the theoretical prediction. Take it with you, and some measuring tape (or the yard lines on the football field) and see what really happens.


The impact location proves to be within 2 meters of the expected value.
When we did the experiment we got a result of 56 meters. That is less than 4% error, very good!

james_lincolnJames Lincoln

Tarbut V’ Torah High School

Irvine, CA, USA

James Lincoln teaches Physics in Southern California and has won several science video contests and worked on various projects in the past few years.  James has consulted on TV’s “The Big Bang Theory” and WebTV’s “This vs. That”  and  the UCLA Physics Video Project.

Contact: [email protected]



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You’re Getting Warmer! [W/Video]

The Little Shop of Physics has developed a series of videos called Flash Science, which show some exciting experiments that can be done with everyday items to demonstrate physics principles in a unique way. All of these experiments have been designed to be done by trained adults using proper safety equipment.


In physics, heat is something you do; it’s a verb. It is defined as the thermal (non-mechanical) transfer of energy. When you heat an object, you transfer energy to it, which can raise its temperature or even cause a phase change. Traditionally, three sources of heat transfer are cited: convection, conduction and radiation.


Radiation is the transfer of thermal energy using electromangetic waves, which includes visible light, infrared radiation, ultraviolet radiation, x-rays and microwaves and radio waves. A camera flash is designed to give off a whole lot of visible light in a short amount of time. The black ink in the newspaper absorbs this radiation and increases in temperature, while the blank paper reflects the light and does not warm up nearly as much.

Conduction and Convection

When a flame is held underneath a balloon, it’s no surprise that the balloon pops. The flame is at a high enough temperature to heat and melt (or even burn) the balloon, and the air under pressure inside quickly escapes. However, when the balloon is filled with water, the flame no longer pops it. The balloon is very thin, and the thermal energy quickly gets conducted to the water on the inside. The water has a very high heat capacity, so it takes a large amount of energy to increase the temperature of the water.

The water is also effective transferring the thermal energy away from the flame. The water will undergo convection; the warm water by the flame will move upwards, and be replaced by colder water coming in from the sides. Also, since water evaporates at 100°C, liquid water has a limit on how high of a temperature it can reach.


Evaporation is an extremely important and sometimes overlooked form of thermal energy transfer. Evaporative cooling is the mechanism behind human sweating, and the energy stored in evaporated water is extremely important in the Earth’s weather system.

In this video the flame hounds are soaked in a mixture of rubbing alcohol and water. While the alcohol burns, and releases thermal energy, the water evaporates and takes much of that thermal energy away from the flame hounds, so that it does not burn!

If you’re careful, you can even hold flaming bubbles in your hands!


Running electricity through the graphite pencil-lead causes the tip to get extremely hot, so hot that the graphite vaporizes and the vapor ionizes. These hot ions are used to cut aluminum foil, similar to how a plasma cutter or arc cutter works.

Erasing With Heat

Some erasable pens use thermochromic ink, which changes colors from dark to light when it is heated. When the ink is cooled (such as through the evaporation of a liquid), the ink becomes dark again. With this ink, you can erase and re-write messages over and over again!


Arbor Scientific’s Video Contest Winners Announced

For ten weeks starting in December 2016, physics educators and their students have been uploading their short videos that capture demonstrations of physics in the world- in Slow Motion. The contest was the first of its kind by Arbor Scientific, the educational leader in finding cool science tools for making understanding scientific principles easy, fun and exciting for today’s students.
Arbor Scientific asked Paul Hewitt, a renowned physics professor and author of the best selling textbook Conceptual Physics*, to review all the video entries and choose the winner. Hewitt said “It has been a pleasure watching these. I chose INERTIA BLOCKS, mainly because of the 4 sheets pulled at the same time; a nice lift to a familiar demo”. The second winner was based upon popular votes at the contest website, receiving over 380 fan votes!


Both winners will receive a $100 Arbor Scientific gift certificate which will help them purchase new classroom science products, a profile on Arbor Scientifics Blog “CoolStuff” and in the CoolStuff e-newsletter mailed to over 20,000 educators monthly.


Amador Valley High School Watch their entry video INERTIA BLOCKS

Amador Valley High School: Students stacked blocks with cardboard pieces attached to string in between. They were able to pull out the cardboard and see that the inertia of the blocks resisted changes in motion enough to stay where they were.

Manistee High School Watch their entry video CONSERVATION OF MOMENTUM


Conservation of Momentum by Manistee High School
Hypothesis: The higher density ball when colliding with a lower density ball will knock the lower density ball back no matter the size. Goal of

Experiment: This experiment was testing how collision is affected by the masses of the objects colliding at the same speed. This experiment also tests and confirms Newton’s Third Law of Motion: For every action, there is an equal and opposite reaction.


  • Four Balls Were Used in This Video:
  • Two basketballs of an equal mass of 600.29g
  • One Volleyball with a mass of 274.19g
  • One Shot Put with a mass of 4200g

A ramp was placed on both sides of the track to launch the balls. The ramp was 7m tall, two people let the ball roll down the ramp at the same time, then observed the results.

There were three trials conducted in this experiment:

  1. First trial: Two basketballs were rolled down the ramp colliding and knocking each other back an equal distance
  2. Second trial: The basketball from the previous trial and a volleyball were rolled down the ramp. The volleyball was knocked back farther than the basketball
  3. Third Trial: The same basketball was used once again and a shot put were rolled down the ramp. The basketball was knocked back significantly by the shot put.

Conclusion: When objects collide the size of the object has little effect compared to the density (Mass) of the object.
“I’m excited for both of our winners,” said Andrea Kelly, Marketing Manager at Arbor Scientific. “They both encompass what we were looking for: presentation, substance and a passion for physics. We surpassed our goal of over 50 video entries and were impressed with the knowledge and creativity all had. We will definitely do similar contests in the near future.”

The submissions can be viewed in their entirety at and will eventually be moved over to the website and blog to remain resources for teachers going forward.

Thanks to everyone for your participation!

*Conceptual Physics Alive! On Demand by Paul Hewitt is online on Vimeo here!



Sound and Waves Demonstrations w/Video


The Mechanical Waves Value Pack is an important addition the laboratory of any teacher who is passionate about the physics of waves or the physics of sound.  The applications for these materials are far reaching and they provide analogies for several topics in Physics, Chemistry, and other sciences.

At the heart of the collection is the Mechanical Wave Driver. This device is very much like a speaker cone, but attaches effectively to all the apparatus in the set.  The driver is powered by the Sine Wave Generator which is adjustable over a wide range of frequencies.

Mechanical Waves Value Pack

The Mechanical Wave Driver and Sine Wave Generator are used in all of the experiments.

A typical experiment which utilizes the driver is Standing Waves on a String.  A string is threaded through one of the fitted plugs for the driver and the other end is tied to a weight.  This is hung over a pulley or smooth surface and its weight provides a near-constant tension in the string.


A variety of standing waves can be produced.  The frequencies will be in simple ratios, in this case 3 to 2.


The wave formulas can be checked against experiment, and usually generate good results.  The wavelength is the distance between two nodes, which are the points that do not move.  The places that move the most are called anti-nodes.  A good lab would be to prove that the product of λ and f  is a constant for a fixed length and tension.  An advanced lab could be to prove that the second formula is valid in any situation.


The Tension is Mg where M is the mass hanging, and L is the length of the portion of string that is vibrating.  However, only the part that is vibrating is to be considered as “m.”  Therefore, it is helpful to know the total mass of the string and the total length of the string.  Then, measuring the unstretched length of the portion vibrating, one can estimate its mass accurately as a fraction of the total string.

3-spring-wavelengthStanding Longitudinal Waves on a Spring is the first accessory that you may wish try out from the value pack.

Attaching a spring to the apparatus will enable teachers and students to demonstrate longitudinal waves.  Standing wave experiments (similar to the string ones) can be performed, including investigating the same wave formulas listed above.  This device can serve as a useful analogy to sound, and students should be informed that all woodwind and brass instruments rely on standing longitudinal sound waves.

4-circlesThe Resonance Wire Loop apparatus provides a new perspective on wave propagation.

Aside from it being interesting, the Resonance Wire Loop device provides an opportunity to show that standing wave propagation does not necessarily mean reflection is involved.  In this case, the waves travel around the loop and cycle back upon themselves.  There is a further application to the mathematics and visualization of electron waves which are also circular waves in the early Bohr / de Broglie model of the atom.


The standing electron waves model helps explain why electrons do not simply orbit any distance around the nucleus, but remain in specific resonant orbits.  Like any standing wave, an electron wavelength that does not resonate would interfere destructively with itself and be quickly canceled.


Students will naturally be confused about how the Bohr atomic shell model is evidence for quantum wave behavior.  But this device clarifies that the origin of the shells is a consequence of electrons behaving as standing waves.  Only integral wavelengths will cycle around constructively.



Another device that serves both as a demo and as an analogy is the metal resonance strips.  These strips will vibrate only at their specific frequencies (and higher harmonics).  The application of this is that buildings can be destroyed when they resonate under the influence of earthquake waves.  For this reason, buildings are sometimes fitted with seismic dampeners which reduce these resonant vibrations.

7-chladni-roundThe round Chladni plate displays waves that are radially symmetric.


Chladni Plates are a classic physics demonstrations that every teacher should have in his or her classroom.  The plate is driven at various frequencies which produce unique wave patterns by moving sand grains away from places of large vibration toward nodal lines (where vibration is minimal). However, because the plate is flat (and not a string) there are many more paths for the transverse waves to vibrate through.  These waves reflect freely off the edges and interfere constructively to create interesting standing wave patterns.

8-juliusJulius Sumner Miller demonstrates that Chladni plates can be driven the old-fashion way, with a violin bow.


The plates can be vibrated with a violin bow, but this is not always available, takes practice, and must be driven in specific locations.  One advantage of bowing is that you get resonances that have the center as a node.  However, the mechanical wave driver offers the advantage of being able to resonate specific frequencies that work best.  Having specific driving frequencies also emphasizes that it is not skill that causes the pattern, but rather the natural resonances of the plate.


The square Chladni Plate can demonstrate a larger variety of patterns because of how the mass of the plate is not constant radially.  As the waves travel out from the center, the amount of mass that vibrates is dependent upon the direction.  This changes the speed at which the waves travel and thus the wavelength (and distance between nodes) thereby creating more intricate and surprising standing wave patterns.   The mathematics of this phenomena is challenging and if you are interested in further study I recommend the following articles from the American Journal of Physics:  Rossing, 50, (1982); Comer, et al, 72, (2004).


Mechanical Wave Accessories Value Pack

In Stock SKU: P7-1500

Mechanical Wave Driver

In Stock SKU: P7-1000

Sine Wave Generator

In Stock SKU: P7-2000

Resonance Wire Loop

In Stock SKU: P7-1500-02

Metal Resonance Strips

In Stock SKU: P7-1500-05

Longitudinal Wave Spring

In Stock SKU: P7-1500-01

Transverse Wave String

In Stock SKU: P7-1500-03

Holder and Allen Key

In Stock SKU: P7-1500-06

Sand and Shaker

In Stock SKU: P7-1500-07


James Lincoln

James Lincoln is an experienced physics teacher with graduate degrees in education and applied physics. He has become known nationally as a physics education expert specializing in original demonstrations, the history of physics, and innovative hands-on instruction.

The American Association of Physics Teachers and the Brown Foundation have funded his prior physics film series and SCAAPT’s New Physics Teacher Workshops.

Lincoln currently serves as the Chair of AAPT’s Committee on Apparatus and has served as President of the Southern California Chapter of the AAPT, as a member of the California State Advisory for the Next Generation Science Standards, and as an AP Physics Exam Reader.  He has also produced Videos Series for UCLA’s Physics Demos Project, Arbor Scientific,,, and


Arbor Scientific Launches Slow Motion Physics Video Contest

Slow motion video capability is an exciting new feature in the latest smartphones and it hasn’t taken long for cool new slow-motion videos to surface, especially in science.

View or Vote


Arbor Scientific has been the leader in finding cool science tools for the past 30 years that make understanding scientific principles easy, fun and exciting for today’s students. “We started this contest as way to enable science lovers like us to easily share our smartphone slow-mo videos that can remarkably demonstrate the physics of so many complex principles. Ideally we want #SlowMoPhysics to become a new free resource available to science teachers to help teach physics in a cool way” says Andrea Kelly, Marketing Manager of Arbor Scientific.

This new slow-motion competition seeks videos from teachers, students and all people who capture demonstrations of “physics” in the world! The contest will accept submissions from December 6, 2016 to January 31, 2017. Also, the public can vote on the submissions at the contest video gallery page found on

The winner(s) will be selected by Arbor Scientific based on originality, popularity and educational value by March 1, 2017 and will receive a $100 gift certificate from Arbor Scientific and the chance to be profiled via Arbor Scientific’s blog and their CoolStuff e-Newsletter mailed to over 20,000 educators.

There also is a specific Teacher Challenge!

Arbor Scientific is encouraging teachers to have their classrooms participate, and get a surprise classroom prize.  See the #SlowMoPhysics Video Contest page for further details.