• Demo Highlight of the Week: Cosmic Rays
  • Last Week's Highlight: Coanda Effect
  • Demonstrations
  • How many demonstrations?
  • New Resource: Directory of Simulations
  • Spotlight: COVID-19 Animation and UMD Research
  • New Resource: Demonstration Video Channel
  • Spotlight: CU2MIP
  • Visit the UMD COVID-19 Dashboard

Demonstration P4-04, the Cosmic Ray Detector, has recently been upgraded. PhD student Liz Friedman shows it in action in this video.


When energetic particles from space hit the upper atmosphere, they create a cascade of particles in the air around us. Even a single cosmic ray might create a whole shower of particles in our atmosphere. They’re invisible, but with the right apparatus we can detect them. Each of the two dark blocks in this device is a scintillator. When a particle passes through one scintillator, it makes a tiny spark of light, which is picked up by a sensitive photodetector. By checking for correlations between the two paddles, we can spot which sparks are being caused by particles passing straight through from space.

These particles stream around and through us all the time, harmlessly; but it’s pretty amazing that we can build a tabletop device that can measure them!

You can read more about Liz’s adventures in physics, hunting neutrinos in Antarctica, in last summer’s Odyssey magazine

Welcome back to the Demo Highlight of the Week! This week, we’re exploring the motion of air with physics student Kathleen Hamilton-Campos and demonstration F5-09, the Coanda Effect with a hair dryer and a ping-pong ball.

Named for Romanian scientist Henri Coandă, the Coandă Effect describes the phenomenon where a stream of moving fluid will tend to stay in contact with a curved surface, and conversely an object in a stream of moving fluid will tend to remain within that stream. While superficially similar to the Bernoulli Effect, which describes the changes in speed and pressure in a constrained fluid, the differences between the two can be important when analyzing things like the movement of aircraft, and in this demonstration! 

 coanda effect diagram, as described in text

A ping-pong ball is placed in the stream of air coming out of a hair dryer. The moving stream of high-speed air entrains the slower air around it, pulling it along. Around the surface of the ball, though, this becomes asymmetric, creating a low-pressure region in the center of the stream with a high pressure region around it. The ball is effectively trapped in this low-pressure core.



We’re often asked how many demonstrations we have in the collection. That’s a more complex question than it might at first seem.

At last count, we have just over 1,500 demonstrations published to the website – that is, that’s how many demonstration pages exist in the collection. But some pages describe a single setup than can be used in several different ways. Take a look at K2-61: Thomson’s Coil, for example. This single page actually describes four different, related demonstrations that can be performed with this device. They don’t require very different equipment to be delivered, just slight changes in preparation, though, and they’re usually all relevant at approximately the same point in a syllabus, so it’s simpler to list them all in one place. Conversely, there are many demonstrations that use the Optical Board – browse through section L and you will see many of them! Since ray optics is divided into several sections in the demonstrations catalog, each of the configurations of the Optical Board is listed separately, to make it easier to find the one you need; and if you’re only doing one demonstration with it, we can configure it for you in advance to save you time in class.

On the other hand, consider M1-12 and H2-22. These are both listings for Interference Transparencies, a popular way to illustrate the interaction of wavefronts. Here, we made the unusual decision to list the same demonstration twice in two different sections, since otherwise someone planning a course on sound might not think to look for relevant demonstrations in the optics section, and vice-versa. These occasional cross-references make it easier to find the demonstrations you need for your class.

And even aside from the demonstration listings as they stand, we’re often called on to combine equipment in unique ways to demonstrate something new! If it’s a combination that’s likely to be repeated or that proves useful to others, it will be added to the website, but we’re generally open to creatively reinterpreting demonstrations to fit a new class context.

Every year we add more demonstrations to the collection; and occasionally a demonstration is retired, if it no longer meets an instructional need or has been superseded by others. So defining just how many demonstrations we have might not be the right question to ask. Ask, rather, what can we demonstrate for you today?

In support of most classes moving to an online model this year, the Lecture-Demonstration staff are doing our part to help connect you to resources you need for teaching remotely. As one part of this project, we have begun compiling a Directory of Simulations from around the internet, organized by general area of physics. Find it under the Tools and Resources menu above, or click the image below.

Sample subsection titles: Electricity & Magnetism Simulations, Mathematics Simulations, Optics Simulations, Oscillations & Waves Simulations, Quantum Simulations, Thermodynamics & Statistical Mechanics Simulations

There are a tremendous number of simulations out there, that folks have been creating for years. We’re testing them out, choosing ones that we can confirm currently work (always a question as internet technology marches on) and that seem useful for our department’s classes. As of this posting, we have just over fifty simulations collected. Our initial focus has been on physics that is hard to demonstrate in the classroom, or experiments that are difficult to present as static pictures or live video.

This project is ongoing! As we continue to explore we will be adding more subjects and more demonstrations per subject. We also invite recommendations! If you have a favourite simulation, let us know (email lecdemhelp at so we can check it out and add it to the directory.

We’ll have more new projects posted soon; watch the site for news!


In our ongoing work to support remote teaching, we are pleased to announce a new resource. Over the summer of 2020, a Teaching Innovation Grant helped to create our new Demonstration Videos. These can be used for remote, hybrid, and in-person classes to present demonstrations in conjunction with class engagement questions.

The videos have their own YouTube channel, linked both here and on the Tools & Resources Menu above; check them out today!


The Conference for Undergraduate Underrepresented Minorities in Physics returns January 8-10, 2021, and we've gone virtual!

cu2mip 2020 ug flyer

Download the flyer today, and visit the website for registration and more information!

CU2MiP is co-sponsored by UMD Physics and NIST.

Science is all about data, and our current pandemic is no different. 

Be sure to check the UMD COVID-19 Dashboard for the latest campus data and links to reopening plans and  proper safety procedures.

Keep Terps Safe - UMD COVID Public Dashboard