Webquest 2 Blog

1. Develop a concept map, which outlines the big ideas addressed in this webquest along with the fundamental concepts, which students should have as prior knowledge.

Students should know the different types of waves but they may not know the terms wavelength and frequency.  I would hope that they already know some basic uses for most types of waves but I doubt that they would know all the astronomical uses for them.  That would be something to emphasize in class.

2. What SC standards (science, math, or otherwise) are related to the teachings/activities in the webquest?

Again there are no state astronomy standards for high school but waves are covered fairly extensively in physical science in Standard PS-7.  The physical science curriculum introduces waves from the ground up. 

Specific to the information in this webquest are the following standards:

PS-7.3:               Summarize characteristics of waves (including displacement, frequency, period, amplitude, wavelength, and velocity as well as the relationships among these characteristics).

PS-7.5:   Summarize the characteristics of the electromagnetic spectrum (including range of wavelengths, frequency, energy, and propagation without a medium).

PS-7.6:               Summarize reflection and interference of both sound and light waves and the refraction and diffraction of light waves.

In my AP chemistry class, waves are covered at the beginning of the year.  It primarily has to do with spectra of different elements which was mentioned in this webquest.  We talk about how exactly electrons absorb and emit energy in the form of photons and calculate frequencies and wavelengths and such. 

The state chemistry standards do not really mention waves, however.  The closest chemistry standard involves electron configuration which is easily taught without even mentioning waves and I rarely mention waves in my non-AP chemistry classes.

3. Using your support documents for these standards, what is essential for students to understand?

Students need to understand that all elements, compounds, molecules, and minerals exhibit specific spectra.  This allows us to determine the composition of objects that are far away by simply looking at the light that they emit or reflect. 

The picture above is of one of my favorite demos to do in chemistry – the flame test.  When salts are heated, electrons jump to higher energy levels because they absorb the heat energy.  When the electrons fall back to their original energy levels, the release that energy in a process called emission.  Electrons of elements emit energy at specific wavelengths which is shown as different colored light.  This is the same concept behind observing starlight to determine the composition of the star or observing light reflected off of the Moon or planets to determine their compositions. 

What we see as visible light is a very small slice of the entire electromagnetic spectrum as shown by the figure below:

Up until just over a century ago, all astronomy was done in only visible light since that was all that the technology of the time allowed.  But now that technology has advanced considerably, we can observe the sky all across the spectrum which yields tons more information.  For example, Saturn’s largest moon, Titan, is the only moon in the solar system with a significant atmosphere.  It is so thick that it completely obscures Titan’s surface so when Voyager 1 flew by Titan back in the 80s, all it saw through its visible light camera was the following:

But when the Cassini craft started orbiting Saturn in the early 2000s, it was able to view in infrared and ultraviolet light which easily penetrate Titan’s smoggy atmosphere.  Cassini returned images like this:

Surface features are easily seen on Titan in nonvisible wavelengths.  Astronomers once thought that Titan had oceans of liquid methane and ethane possibly miles deep but they’re probably more slushy.  And I’m pretty sure that they have confirmed methane and/or ethane rain which I think is awesome.  It’s the only other body in the solar system with a weather cycle that has liquid in it.

4. How can the materials/information be used to help students develop their essential understandings?  How can you modify the information or lesson to address the development of these understandings?

The best activity in this webquest was looking at solar spectra and identifying elements present in the Sun.  I think that the students would learn a lot by doing a similar activity and it could be presented as a game in which they compete against each other. 

Also, comparing the Moon in different wavelengths would be useful.  I especially would like to show the visible and infrared pictures of the near side of the Moon and have the students explain the differences. 

5. What key misconceptions commonly inhibit a clear and accurate understanding of this content?  How should you modify your instruction to address these misconceptions?

A somewhat common misconception that students have about waves is that they think that waves with long wavelengths, mostly radio and micro, should be visible since the wavelengths are as long as houses and mountains.  While technically we can see waves since we see light, we can’t see the crests and troughs of waves because the amplitudes are so small.  Our eyes can’t see things nearly that small so we see light as a beam rather than a wave.

And one of my favorite misconceptions is when people say that radiation is harmful.  The majority of the electromagnetic spectrum (radio, micro, infrared, and visible) is harmless.  We are exposed to ultraviolet every day we step outside on a sunny day and while too much is not good, ultraviolet light is helpful in producing some kind of vitamin in our skin I believe (I’m not entirely sure which though).  X-rays and gamma rays are pretty harmful but Earth’s atmosphere absorbs them efficiently.

I show the movie “The Core” in my astronomy class when we talk about the Earth system and the students’ assignment is to write down all that is scientifically wrong with the movie which usually takes the front and back of a sheet of notebook paper.  The scene of The Core depicted below is of the Golden Gate Bridge in San Francisco Bay being destroyed by microwaves from the Sun. 

While microwave radiation can heat water, the Sun does not put out concentrated beams of microwaves as depicted above.  And microwaves aren’t blocked by the Earth’s magnetic field anyway since they aren’t charged particles which completely flies in the face of the movie’s premise that the collapse of Earth’s magnetic field would allow lethal microwave radiation to kill everybody.  In fact in my astronomy class last year, it was a running joke all year long that although black holes and gamma ray bursts and the Sun swallowing up Earth as it becomes a red giant could all eventually kill everybody on Earth, it's deadly microwaves that we have the most to worry about.

6. What new scientific information did you learn in this lesson?

I know a fair amount about light and waves and such since it is covered fairly extensively in physical science which I used to teach.  It’s also a big unit in AP chemistry so I really had to learn it in detail before I started teaching AP.  Even with all that, I had no idea that red and blue light corresponded to electric fields and magnetic fields, respectively.  I remember from college physics that electric fields and magnetic fields are perpendicular and I’m pretty sure that the right-hand rule is involved somehow although I can’t remember how exactly.  Spectra are used occasionally in AP and I always tell the story of how a spectrum of an unknown element was discovered in sunlight.  The element was named helium after helios which is the Greek word for the Sun. 

7. What questions do you still have?  (Write at least two and answer them with the resources and links provided.)

How are electric field and magnetic fields related?  I know it involves the right-hand rule and after looking it up, I found the diagram below.

When electricity passes through a wire in the direction indicated by the thumb, the fingers curl in the direction of the magnetic field lines induced by the electric current.  A magnetic field can also induce an electric current. 

What is the source of x-rays on the dark half of the Moon in the picture below?

I looked this up at http://chandra.harvard.edu/photo/2003/moon/more.html and it says that the x-rays on the dark side are due to Earth’s geocorona.  I have never heard that term before so I had to look it up.  On http://pluto.space.swri.edu/IMAGE/glossary/geocorona.html, it says that the geocorona is sunlight reflected off of Earth’s exosphere which is the outermost layer of the atmosphere.  The x-rays in the sunlight reflect off of Earth’s exosphere which in turn reflect off of the Moon then are detected by satellites orbiting Earth.  Those dots went through a lot to be in that picture.

8. What new instructional practice did you learn?  Describe how you can use this in the classroom.

I didn’t know that it was possible to make my own spectrometer.  It works ok with lightbulbs but I think tomorrow I’ll go outside and look at a cloud to see what it looks like.

I’m not sure if I will do this in class because it would take a lot of time to illustrate a simple concept that can otherwise be explained in simpler ways.  I can use a prism to show how light can be split into different wavelengths.  Then we can do the flame test demonstration to show how different elements emit specific wavelengths of light.  These two activities are combined in making the spectrometer but both are simpler to do separately. 

However, I might make it an AP chemistry project though to do after the AP exam.