Tuesday, February 16, 2010

Measuring Microwaves with Chocolate

I wrote up our latest lab as a post for GeekDad, and it ended up going popular on Digg! (For those who care.) To see how we measured the speed of microwaves with a chocolate bar, follow the link.

However, we did several trials, so here are some photos from our earlier attempts. And yes, the scale did go up in the last few days...
We only got only hot spot with this one ... and the paper plate started to burn (note lower right corner).

We tried multiple bars to get broader coverage. This worked a little better.

A dish full of chips provided the best coverage of all, but was too hard to pinpoint the hot spots. After several minutes of microwaving, we got one fused, hard point of chocolate (indicated by spoon) but not a second spot to measure. 

The results:
Best holder: glass baking dish
Best stand (to cover the rotating thing in the microwave): small plate
Best chocolate: Valentine's Day cherry cordials

This experiment has also been done with marshmallows and by kids on YouTube

Friday, February 12, 2010

Big Blog Theory

If you are a fan of The Big Bang Theory -- and I don't watch near as often as I should -- then you will enjoy the blog of UCLA particle physicist David Saltzberg, who is the show's consultant. The Big Blog Theory explains the science behind the episodes.

The show can be seen on CBS Monday nights at 9:30 EST.

Hat tip to a post by fellow GeekDad writer John Booth.And for other interesting physics blogs, check the list way down in the sidebar.

Tuesday, February 9, 2010

Wave Lab Part 2

After watching some cool videos on YouTube, I decided it would be fun to make patterns with sound waves. These patterns are caused by the same kind of waves, and wave interference, that we saw with our pseudo-ripple tank experiment. Again, our setup was crude: we took a recycled container and set it over a tiny set of speakers and an mp3 player loaded with video game soundtracks. Then we sprinkled some salt on a plate and put it on top. We also tried sprinkling salt directly on the metal top, and then tried it with some water.

We didn't always get fancy patterns, but we did see some nice movement. Watch!

In the videos on YouTube done with real lab equipment, you can see cool Chladni patterns.

Here's an explanation from Teacher's Domain:

When an object vibrates at one of its natural frequencies (a rate of vibration at which it naturally tends to move), standing wave patterns are formed within the object. These patterns are the result of wave interference, which occurs at the meeting of two waves traveling within the same medium in different directions. The resulting disturbance within the material at the point where the waves meet is the net effect of the two waves. At certain points in the material, the waves cancel each other out through destructive interference and there is no net disturbance. These points are called nodes, or nodal points. Around the nodes, the waves constructively interfere; the points with the greatest disturbance are called antinodes, or anti-nodal points.
And here's an explanation of their origin and use from Robert Krampf:
These patterns are called Chladni patterns, named after Ernest Florens Friedrich Chladni of Saxony, who has been called the father of acoustics. He sprinkled sand onto metal plates and studied the way that they vibrated.

Besides being fun to play with, these patterns are useful. These patterns are used in designing musical instruments. If a part is attached to a place where the instrument vibrates, the sound will be dampened. By attaching parts at nodes, the instrument makes a full, rich sound. These patterns make the difference between an average instrument and a quality one.

Here are the rest of our videos:

Saturday, February 6, 2010

Book Review: How to Teach Physics to Your Dog and The Macroscope

(I wrote this article for the Albany, NY Times Union newspaper. It originally appeared, in edited form, on January 24, 2010.)

When you think about it, “modern physics” isn’t really all that modern anymore. Einstein began drafting his theory of relativity in 1905, and quantum mechanics – which describes how things work at the sub-atomic level – was described by Max Planck in 1900. Today quantum mechanics is at the core of everything from bar code scanners to computer chips. It’s the most accurately tested theory in the history of science.
And yet very few people are aware of even its most basic concepts. Ideas like particle-wave duality (the fact that light and matter has both wave and particle nature) are rarely covered in college physics classes, let alone high school. So when Internet rumors claim that the CERN Large Hadron Collider, which smashes atoms together to see what pops out, is about to suck the Earth into a black hole, or when the latest DaVinci Code book features a physicist who uses “thought particles” to transform matter, most people don’t know what to believe.

That’s a gap two new books by local educators are hoping to bridge. In “How to Teach Physics to Your Dog,” (Scribner, 2009) author Chad Orzel explains quantum mechanics to Emmy, his German Shepard mix, in language so down-to-Earth and entertaining that even humans can understand. Why a dog? As Orzel, an associate professor in the department of physics and astronomy at Union College in Schenectady, explained recently, dogs have no preconceptions about where things come from. That makes it much easier for them to accept the idea of virtual particles and parallel universes.

“As bizarre as it seems to a human, as far as a dog is concerned dog treats appear out of the air,” Orzel said. “She will sit there staring, hackling at evil squirrels from another dimension.”

For readers, following Orzel as he discusses the probability of bunnies made of cheese suddenly appearing in the backyard, or whether dogs can use their wave nature to pass around both sides of a tree at the same time, makes modern physics easier to understand.

“As scientists,” Orzel said, “we speak about it in math. I wanted to find ways to get around that, to show how fascinatingly weird the world is without forcing them to go through three years of physics.”

At the same time, Orzel added, “There is some heavy stuff in the book -- decoherence, ‘many worlds’ theories – that you don’t often encounter in popular treatments of the subject. The nice thing about writing with the dog is that whenever things get a bit thick, I can have her break in.” At those times Emmy pipes up to remind Orzel, “I don’t want to describe the universe, I want to catch squirrels.”
The goal for Orzel is to help readers understand that although the universe is a really strange place, it still has rules, and physicists have been sucessful so far in understanding them.

“You can’t will yourself into another universe where you’re wealthy,” he said. “I hope the dog is cute enough to carry people past some of the need for it to be magic.”

While Orzel’s book was written for adults whose schooldays are behind them, “The Macroscope,” the first in the Adventures in Atomville series, aims to inspire kids who have yet to set foot in a physics classroom. It’s a fantasy story in which all the characters are atoms which behave in ways that reflect the properties of their particular elements. They eat (and emit) photons, and swat away pesky electron gnats. But the physics is hinted at, not explained outright. (A website explaining the science behind Atomville is under development.) Co-authors Jill Linz, a senior physics teaching associate at Skidmore College in Saratoga Springs, and Cindy Schwarz, a professor of physics at Vassar College in Poughkeepsie, both said that the plan was to pique kids’ interest, not lecture to them.

“We don’t necessarily want these kids to walk away knowing what’s going on with subatomic particles,” explained Schwarz. “We want them to keep the words in the back of their heads and feel more comfortable when they hear them again.”

Linz first developed Atomville as a way to reach non-science majors, and later went on to produce physics videos for elementary schools. Schwarz uses creative writing and music in her physics classes for non-majors, and has published a book of her students’ physics poems and stories called Tales from the Subatomic Zoo.
Linz and Schwarz are hoping schools will invite them in to talk about their book and about physics. Last spring Schwarz showed students in Poughkeepsie how atoms emit photons and letting them look through diffraction glasses to see the spectrum created by an element. She was happy to find that, months later, they still remembered the concepts they learned.

“They really got something out of this,” she said.

Friday, February 5, 2010

Wave Lab Part 1

Having read the wonderful book How to Teach Physics to Your Dog by Union College professor Chad Orzel (post to come), which talks about the conundrums posed by lighting behaving as both wave and particle, I decided to do a series of labs dealing with waves and leading up to some demonstrations of wave/particle duality

We started out looking at the interference pattern created by splitting a laser beam (again, post and photos to come). But then I decided it would be helpful to go back and look at plain wave behavior. So I backtracked and did two simple demonstrations of waves -- one with water, one with sound.

For the water demonstration I made a very crude approximation of a "ripple tank." I took a shallow, dark colored plastic storage box, filled it with water, and created wave patterns with two spoons. We soon found that shining a light directly on the box made it easier to see the waves via the shadows they made. Although one source suggested tapping the water with the back of the spoons, we also found that we got better results by scooping up a little water and pouring back into the tank.

We observed how one wave moved away from the source (the drip) and then bounced back off the walls of the tank. Two simultaneous waves intersected and created a pattern with stronger crests and troughs (highs and lows) where they either added together or canceled each other out.

Here's a video of a real ripple tank courtesy of the Carleton University's YouTube Channel:

Stay tuned for Wave Lab Part 2: Sound Waves, coming soon!

Wednesday, February 3, 2010

Cycling Physics -- Watch a physics teacher in action

I've got a post up on GeekDad today about Florida physics teacher Luther Davis, who will be riding his bike in his classroom for 7 hours tomorrow. While he's pedaling, he’ll have his students stream his bike ride/physics lesson live from the classroom and take questions via online chat.

Update! Update! Update!

Davis achieved his goal, pedaling 143.1 miles in 7 hours (while teaching), and raised more than $1,600 for the American Diabetes Association. Great Job Luther!

We got to watch Davis talking about angular and linear momentum, and even asked some questions via the chatroom. It was pretty cool! His website Cycling Physics now shows graphs of speed, heart rate, and cadence (pedal rotations per minute) for his ride. Video segments will be available soon.

We wish Davis luck when he undertakes the ADA Tour de Cure in Orlando on February 28, 2010.

We also challenged Davis to join us here in Upstate New York this summer for the Saratoga 12/24 and Adirondack 540 bike races (presented by Adirondack Ultra Cycling, aka my husband, John Ceceri)!