Posts Tagged ‘light’

Light & Waves by Dot Physics

Another great post by Rhett at Dot Physics! It’s always difficult to teach the wave-particle duality of light since students (and even teachers) struggle with the abstract reasoning involved. Rhett does a fantastic job with his illustrations and explanations of light as a wave. I’m definitely using this with my students.

Read the article “Light and Waves – at a basic Level”

Mystery Circuit Box

I found an article about mystery circuit boxes several years ago in The Physics Teacher. I’ve recently had the opportunity to actually use it in a lesson!

Martha Lietz (the author of the lesson I based mine off of) uses rewired bathroom beauty bar lighting in order to teach her students about series and parallel circuits in reverse. Basically, students are given a strip of lights and unscrew the light bulbs one at a time to deduce how the circuit is wired.

I decided to take it one step further and use mystery circuits to assess students’ knowledge of circuits using various wirings of circuits in the different beauty bars in order to evaluate how well students understand the differences and effects of series and parallel wirings. You can view my lesson plan here.

One of the greatest parts of this demonstration is that the materials are easy to find and relatively inexpensive. I found the beauty bar at Lowes (or Home Depot) for around $13. I also had to by a wire cutter/stripper and extra wire nuts. Plus, you can use them over and over again!! I recommend using 40 watt rated bulbs or less because they get hot rather quickly.

One of my mystery circuits was the one designed by Lietz, and I’ve included pictures here. Can you figure out how it’s wired?

Picture One: All bulbs are screwed in tightly. Bulb one is the brightest, bulbs two and three are the dimmest but shine to the same intensity, and bulb four has a brightness right in the middle of the others. NOTE: It is important to be sure that a bulb’s brightness is due to the power it receives from the circuit and not simply a reflection of light from the bulb next to it. This was the major point of confusion for students with regards to bulb two.

Mystery Circuit 1

 

Picture Two: Bulb one is unscrewed and all bulbs go out.

Mystery Circuit 2

 

Picture Three: Bulb two is unscrewed. Bulbs one and two are the brightest and bulb three goes out.

Mystery Circuit 3

 

Picture Four: Bulb three is unscrewed. Bulbs one and two are the brightest and bulb two goes out.

Mystery Circuit 4

 

Picture Five: Bulb four is unscrewed. Bulb one dims slightly. Bulbs one, two, and three all shine at the same intensity.

Mystery Circuit 5

 

Using the information and pictures provided above, can you figure out how the circuit is wired??

Corks, Ears, and Eyes, Oh My!

I recently read this question, I’m curious to hear what you think!

Someone (maybe Helmholtz) suggested the following way of thinking about how our eyes and ears interpret light and sound. Imagine that you are standing at the edge of a lake. If you use your eyes, you can get an enormous amount of detailed information about the lake and its surroundings: trees on the shore, birds on the lake, cars and trucks traveling on a road nearby…. However, suppose you could only look at two corks floating side by side near you on the surface of the lake. How much could you deduce about the lake and surroundings by simply observing and interpreting the movements of the two corks? In fact, that is what your ears (and brain) do if you think of your eardrums as the corks!

Explain and evaluate the validity of the contrast between seeing and hearing described above. What characteristics and properties of light and sound does it depend upon? What is (or are) the key difference(s) between the behavior of light and sound, and between the operation of our eyes and ears, that give rise to the dramatic contrast between seeing and hearing described in the above paragraph.

Please leave your comments!

Solar Ovens

A friend just sent me this article from CNN about a dad and his daughters making a solar oven.

What a cool project!

Since it peaked my interest, I found a website to make your own solar oven.

If you do decide to make one with your class (or at home!), here’s a list of solar oven recipes.

Reasonably Priced Laser Pointers

I was browsing the internet dreaming of getting a shiny laser pointer :o)

What I stumbled upon made me think about getting one now!!!
Amazon.com’s listing of laser pointers is incredible (can be found HERE). I was most impressed that the green lasers, which are usually priced in the hundreds of dollars range due to the expense of manufacturing them, were between $30 and $50!!!
If you’re in the market for a laser pointer, check out Amazon.com!!
**Lesson ideas for laser pointers coming soon!

The Color of Light

I saw a great demonstration the other day in class about the color of light. It is similar to a lesson plan found at: http://science.hq.nasa.gov/kids/imagers/teachersite/UL1.htm


To begin, my classmates drew two venn diagrams. One had the colors of paint (red, yellow, and blue) and the other had the colors of light (red, green, and blue). We guessed which colors created which new colors (orange, green, purple and yellow, cyan, and magenta, respectively).
Next, they turned on three light bulbs (a red, green, and blue one). All other sources of light was covered and a large white projection screen was against one wall. One classmate put a meter stick in the way of the light and in front of the screen. It was amazing to see the meter stick separated the light into yellow, cyan, and magenta. Then the light bulbs were turned off one at a time. When the red light bulb was turned off, the background of the screen was cyan, while green and blue were separated by the meter stick. Similar results occurred when the green and blue light bulbs were turned off. 

It was just amazing!! Try it at home if you don’t believe it :o)