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The Physics Girl: Standing Waves on Chladni Plates

Do you know that you can use physics to create cool patterns on a vibrating metal plate? The Physics Girl demonstrates how. So tune in to see and hear some amazing physics about vibrations, waves, and resonance.

https://www.youtube.com/watch?v=wYoxOJDrZzw

And if you want to learn more about the resonance and standing waves, then visit our Tutorial page on the very topic at ...

http://www.physicsclassroom.com/class/sound/Lesson-4/Standing-Wave-Patterns
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Children's Science Series: 15 Things to Build & Create Using Newspapers

Why go out and spend money on building materials when you have some great stuff around the house, right! Newspapers are easy to come by and usually just recycled once read. Why not turn them into a few high fun, low cost summer projects for kids! With the ideas at this website, you can do just that. There are 15 engineering ideas relying upon newspapers. Build an Eiffel tower, a geodesic dome, a pyramid, and more. Find out how at …

http://www.kcedventures.com/blog/15-things-to-build-create-using-newspapers
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Physics That Resonates with Everyone

In the late 18th century, musician and scientist Ernst Chladni demonstrated the two-dimensional vibration of a flat plane caused by certain sound waves. Following in the footsteps of Robert Hooke, Chladni drew a rosined bow across the edge of a sand-covered metal plate. When the bow created certain frequencies of vibration of the plate, the plate resonated with beautiful vibrational patterns like those shown here. Visit science writer Joe Hanson's It's OK to Be Smart blog to learn more and to view some videos of the phenomenon.

http://www.itsokaytobesmart.com/post/27927640271/chladni-patterns-acoustic-science
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Do Cell Phones Cause Brain Tumors?

It's a fair question! And I wouldn't draw a conclusion too quickly. Because if cell phone radiation does cause cancer, a whole lot of us are in trouble. Join Derek Mueller of the Veritasium YouTube channel as he "takes it to the streets" and dissects the various studies and possible means by which this question can be reliably answered. Join Derek at ...

https://www.youtube.com/watch?v=wU5XkhUGzBshttps://www.youtube.com/watch?v=wU5XkhUGzBs

And for the teachers among us: why not make plans to present the question to your classes using the Science Reasoning passage present at our website that is titled Cell Phone Radiation. The passage presents both sides of the question to students and challenges them to analyze the arguments and draw some conclusions.

http://www.physicsclassroom.com/reasoning/light

We recommend that you challenge your students to the Reading Passage first and then use the Veritasium video as the follow-up.
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Let's Make a Wave

One of the more popular exhibitions of a wave is the so-called "Stadium Wave." Pile several thousand people in a stadium and have some cheerleaders direct the action of "doing the wave." A visible ripple travels from seat to seat as stadium-goers stand up and sit back down in consecutive fashion. Today we present the military version of the stadium wave. Visit out Pinterest site at

http://www.pinterest.com/pin/487373990898879244/

A tap on the Pin leads to its source at

http://giant.gfycat.com/SociableSameIriomotecat.gif
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Solution to Yesterday's Physics Puzzle

Yesterday's post presented a puzzle on the topic of color. The puzzle involved identifying the color of the three lights that were used to produce the elaborate collection of colored shadows projected onto a whiteboard. Which is red? Which is green? And which is blue? The answer to the puzzle is: 1 = Green … 2 = Blue … and 3 = Red.

In the photo, the person figure is blocking the light sources. Shadow section A is colored cyan. Cyan light results when blue light and green light are mixed with equal intensities. Shadow A results when light from Bulb 3 is blocked by the person figure but light from Bulbs 1 and 2 pass by the person and reach the whiteboard. Thus Bulbs 1 and 2 are green and blue; one of them is the green light and the other is the blue light.

Similar reasoning leads one to conclude that shadow section E – the magenta section results from light from Bulbs 2 and 3 reaching the whiteboard. Since magenta light results when red light and blue light are mixed with equal intensities, one must conclude that Bulbs 2 and 3 are red and blue. One of the bulbs is red light and the other is blue light.

So the above two paragraphs of reasoning lead us to the conclusion that …

Bulbs 1 and 2: one bulb is green and the other bulb is blue.
Bulbs 2 and 3: one bulb is red and the other bulb is blue.

From this we can conclude that Bulb 2 must be the blue bulb. And that means that Bulb 1 must be the green bulb and Bulb 3 must be the red bulb.

Finally, we can test these conclusions by looking at Shadow sections B, C and D. Shadow section B results when light from the Green Bulb 1 passes by the person figure and reaches the whiteboard. This explains why Region B is lit with green.

Shadow section C results when light from both the Green Bulb 1 and the Red Bulb 3 pass by the person figure and reaches the whiteboard. Red light and green light combine to form yellow light. This explains why section C is lit as yellow.

Finally, shadow section D results when light from Red Bulb 3 passes by the person figure and reaches the whiteboard. This explains why section D is lit with red.

To explore these concepts further, try the Colored Shadows Interactive at our website:
http://www.physicsclassroom.com/Physics-Interactives/Light-and-Color/Colored-Shadows

or take a visit to our Color Lesson in our Tutorial:
http://www.physicsclassroom.com/class/light/Lesson-2/Color-Subtraction
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Can You Solve this Physics Puzzle?

Consider the following set-up: A straw is inserted into a stopper so that it stands upright on a table. A figure of a person is taped to the straw. A whiteboard is mounted vertically to the table behind the straw and person figure. Three lights – red, green and blue – are placed side-by-side to illuminate the figure. Because the person figure blocks the light, three shadows are cast onto the whiteboard. Because the lights are colored lights, the shadows are colored shadows. And some of those colored shadows overlap, giving rise to even more color. The set-up is shown in the diagram on the left. The results are shown in the photo on the right.

What colors are lights 1, 2 and 3 in order to produce the photo that is shown? Leave your answers and discussion as a comment.

Tune in tomorrow for the answer and explanation.

Need help? Try the Colored Shadows Interactive at our website:
http://www.physicsclassroom.com/Physics-Interactives/Light-and-Color/Colored-Shadows

or take a visit to our Color Lesson in our Tutorial:
http://www.physicsclassroom.com/class/light/Lesson-2/Color-Subtraction
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Grooovy! Standing Wave Maker

Our Standing Wave Maker Interactive is an adjustable-size file that displays nicely on smart phones, on tablets such as the iPad, on Chromebooks, and on laptops and desktops. You can set the frequency, wavelength, wave speed, and amplitude..... then kick back and learn physics while you watch the pattern. The size of the Interactive can be scaled to fit the device that it is displayed on. The compatibility with smart phones, iPads, other tablets, and Chromebooks make it a perfect tool for use in a 1:1 classroom.  Don't forget to say "Groovy" while you run it!

Find the Standing Waves interactive HERE:   http://bit.ly/1JWDInY

And here's a Teacher's Guide to go with it:  http://bit.ly/1DH72cY
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Can You REALLY Break a Wine Glass with Sound Waves?

Professor Mark Miodownik finds the resonant frequency of a wine glass, as indicated by the small vibrating slip of paper balancing on the edge. When he cranks up the volume, the glass oscillates so strongly that… crack!! It's real. No Fooling. See for yourself at The Kids Should See This website:

http://thekidshouldseethis.com/post/dara-o-briains-science-club-breaking-a-glass-with-sound

And if your wish to learn more about the Physics behind the phenomenon, then visit our Tutorial page on the topic of Resonance at ...

http://www.physicsclassroom.com/class/sound/Lesson-5/Resonance
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Physics Gallery on Light and Color

As it is said, "A picture is worth 1000 words." And from this statement we reason that "A gallery of pictures is worth a chapter of text." And that's exactly what you will find in the Gallery section of The Physics Classroom's Flickr site. Today we would like to call your attention to our eye-catching gallery on the topic of Light and Color. We have gathered 8 striking photos from some exceptional photographers and accompanied them by some informative text in order to tell the story about the physics of color. Enjoy the gallery at:

https://www.flickr.com/photos/physicsclassroom/galleries/72157625110255449/
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