Simple Polarimeter

This DIY device is part of the polarization kit that you will get from a MEL Physics subscription:

Subscribe to: MEL Physics

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Simple Polarimeter: Two linear polarizing sheets oriented at 90 degrees creates this device that reveals rainbows hidden within the patterns of polarization in the light transmitted by some common plastic objects. Just one of many amazing experiments from the MEL Physics science kit collection. Polypropylene is a clear transparent plastic comprised on long chain like molecules which interact with light wave orientation- when this plastic substance is heated to form things like utensils or containers, these long strand molecules lock in pattens of stress from the cooling, which are revealed as changes in color/frequency of the transmitted light.

PDLC Electric Field Induced Transparancy

Get this device here:

From Amazon: BUY NOW: PDLC Smartwindow Sample

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and click here for the balancing dragon toy

PDLC Electric Field Induced Transparency: when a voltage is placed across Polymer-Dispersed Liquid-Crystal film, long skinny molecules align with the electric field allowing light to pass through without scattering- with the field off the molecules thermally randomize and then do scatter the light passing through, producing a milky white translucent appearance. This sample of a “smart window” is powered by a 1.5 Volt AA battery and has very thin metallic coating on the front and back. A fun demonstration of electrochromic materials. 

Magentic Dandelion 

Here is a very powerful NdFeB neodymium magnet that will work withlarger nails: 

From Amazon: BUY NOW: Neodymium Disk Magnet

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Please use extreme caution when handeling strong magnets like this one. Small nails, paperclips, staples and other houlshold object made with iron will interact interestingly with the magnetic field. 

Magnetic Dandelion: through ferromagnetic interaction these iron rich nails temporarily become dipole magnets in the presence of an intense magnetic field from a neodymium super magnet. Here the neodymium disk magnet is set with its north pole pointing up, so the point of each nail becomes a south pole (repelling each other) and the head of each becomes a north pole. Imbued with these temporary induced fields, the nails will try to align themselves with the neodymium dipole’s field like compass needles, and the nails will interact with each other in interesting ways. 

Fluorescein v. Laser Frequency

Need a laser pointer? Incredibly, you can get 3 (one of each color) for under $20 (including S&H): 
From Amazon: BUY NOW Red+Green+Purple Laser Pointer

Make you own fluorescent solution with this powder: 
From STEMCell Science: BUY NOW: Fluorescein Powder

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Fluorescein v. Laser Frequency: exploring how this famous fluorescent dye reacts to three frequencies of laser pointer using this unique liquid filled paperweight. Under Green (532 nm) we see some mild yellow fluorescence as the beam transmits through the liquid, under Red (635 nm) the beam transmits with no reaction, but under near UV Blue (450 nm) the beam is completely absorbed near the liquid surface and re-emitted in bright green with a peak at 515nm. A fun home experiment to explore quantum physics phenomena with inexpensive apparatus.

Solenoid Magnetic Accelerator

Get this and similar devices here:

From EngineDIY: BUY NOW: Steel Ball Cyclotron Accelerator

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Solenoid Magnetic Accelerator: six electromagnet coils push a steel ball to terminal velocity. Each coil is triggered to briefly energized only when an infrared led and sensor circuit detects the presence of the ball. The steel ball’s speed seems limited by the strength of the temporary magnetic field and the friction it encounters from the track. This ring configuration demonstrates proof of concept for a means of accelerating steel marbles and I hope to incorporate these coils in other marble run designs I will share in the future. Uses a 12V power supply. 

Horseshoe Magnet with Keeper

Similar and affordable magnets available here:
From Amazon: BUY NOW: Horseshoe Magnet with Keeper

Get some viewing film here:
From Amazon: BUY NOW: Color Magnetic Viewing Film

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Horseshoe Magnet with Keeper: magnetic field lines connect North to South poles from one side of the U shaped magnet, through the air, to the other- and magnetic viewing film reveals the strong fields of this vintage magnet. However, when a bar of soft iron is attached, the magnetic field lines prefer to pass through the bar, and the field is then concentrated in the bar and significantly reduced in the surrounding air- basically shutting off the field around the magnet as seen by the viewing film. Such a bar is called a “keeper” which serves to contain the field and also persevere the strength of the magnet when not in use.

Rolling Uphill Illusion

Availabel here:
From Etsy: BUY NOW: Uphill Ramp Illusion

or get the 3D print file here:
From Thingverse: Download Now: Uphill Illusion

Learn more: The amazing illusions of Kokichi Sugihara
See the many other Sugihara Illusions: in my collection

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Rolling Uphill Illusion: the ball bearings seemingly roll uphill as if attracted by magnets of some kind. What’s going on? Swipe for reveal as it is truly a matter of perspective. A wonderful take on an illusion invented by Kokichi Sugihara of Meiji University. 3D printed by my good friend @zathras5 (Roger Key) from a file designed by Julian Hardy. 

Electric Motor Build

Get an easy to assemble kit here (or just buy the replacement wire to build your own like in the video): 
From Educational Innovations: BUY NOW Simplest Motor Kit 

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Electric Motor Build: One of the most important inventions consists of only three basic components as shown here: coil, magnet, and a battery with lead wire posts. The wire of the spinning coil has an insulating coating on it- and this coating is carefully scrapped off one side of the thin wire on each end. When current passes through the coil it becomes an electromagnet and the permanent magnet repels it making it spin- as it turns the current goes on and off depending on if the copper wire posts are in contact with the bare wire side (current on) or the part of the wire with the insulating coating intact (current off). When the current is off momentum keeps the rotation going until the next push. The physics of converting electric energy to rotational kinetic energy- and a fun DIY project! 

Wireframe Ambiguous Cube

Get the files (or order one printed) here:
From MakeAnything's MyMiniFactory: BUY NOW: Illusion Cube 3D Print Files
From Shapeways: BUY NOW: Ambiguous Cube Illusion

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See the other illusions my collection: Ambiguous Objects

Wireframe Ambiguous Cube: another innovation of the ambiguous object illusion invented by mathematician Kokichi Sugihara of Meiji University- this time a 3D frame of a cube transforms to a cylinder! A new 3D print design from @make.anything

Repelling Marbles Puzzle

Get this affordable and fun kit here:

From Educational Innovations: BUY NOW Mystery Marbles Puzzle Kit 

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Mystery Marbles Puzzle: a physics brain teaser (now available as a kit) what's going on here? Three glass marbles can move but stay separated in this liquid filled tube no matter the orientation- why do they not touch? Swipe for reveal of components. 

See also: Poly-acrylamide Polymer Vanishing Act

Compliant Mechanical Elephant

Get the .stl files for this 3D print here:
From Thingiverse: Download NOW: CM Elephant

Learn more: mechanical engineering of compliant mechanisms

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Compliant Mechanical Elephant: a demonstration of engineering using flexible elements instead of pivot joints when creating linkages. In this whimsical and clever linkage design a sideways translation of the elephant creates only rotation at the tip of the pachyderm’s trunk. Note that the hole at the end of the trunk remains eerily stationary as the body translates horizontally back and forth. This demonstration model comes from the Compliant Mechanisms Research group at Brigham Young University. Thanks once again to Roger Key for producing this 3D print. 

Harbottle Air Pressure Demonstration 

This item came to me in my Spring 2022 Curiosity Box subsciption:
Get (or give!) a Curiosity Box subscription here: JOIN NOW: The Curiosity Box

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Harbottle Balloon Demo: a regular untied balloon remains inflated- one can even look down the neck of the balloon and see inside! Just blow up the balloon inside the bottle and then cork the hole in the opposite end- in so doing the inside of the balloon is experiencing the full force of air pressure, but the exterior of the balloon is protected from the crush of air pressure by the rigid wall of the bottle. Air pressure at sea level is 10.1 Newtons of force per each square centimeter of area (14.6 pounds per square inch). The bottle allows a pressure differential, pressure on the inside but much less on the outside of the balloon. Take the cork out- now both sides experience the same air pressure and the elastic force is no longer balanced. A fun demonstration reminding us that we live at the bottom of a deep sea of atmosphere!

"Impossible" Domino

Get the 3D print files here:

From Download Now: Impossible Domino

This video from The Action Lab has a good decription of rhe physics. 

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“Impossible” Domino: a pair of specially engineered domino type objects where the right domino knocks over the left one, but then stands back up! When seen in slow motion the process becomes more clear. The main factor here is that the center of mass of the left domino is higher than that of the right one, giving it much more potential energy so when the left one topples over it can transfer some energy back to the right one. Created by the folks at viralvideolab and 3D printed by my friend Roger Key (thanks!)

Single Strand Tensegrity

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From Thingverse: Make Now: Single String Tensegrity

Click here for more tengerity in my collection.

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Single Strand Tensegrity: a vertical chain- when held under tension a single length of thin chain can become a rigid support structure. In this design four 3D-printed struts each act like an archer’s bow to stretch the chain under tension. Beads placed on the chain interlock with the ends of the struts. Design and .stl files by Ernie Condone and printed by Roger Key (thanks!)

Vortex by Lava Lamp

A DIY kit by the makers of Lava Lamp, home experimentation set with booklet of ideas to try:

From Amazon: BUY NOW: Lava Lamp LED Vortex kit

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Vortex Lamp: a simple whirlpool powered by a magnetic stirrer like those in a chemistry lab and lit by LEDs. A DIY kit by Lava Lamp brand- which comes with glitter and beads, but I found the water vortex alone was mesmerizing to watch. Note the intricately changing structure of the vortex in the slow motion close up.