Light and Water: Post Eleven

Here's another example of a surface acting like a mirror, made particularly interesting by the fact that some objects are behind the table, and some objects are on the table.

Question of the Day: Why does Joe Biden's hand look so much closer to the other guy's chin in the reflection than it does in reality?

What's the first question that come to mind?

WCYDWT: Rought Sketch of Possibilities

There has been an explosion of dandelions in Maine, and I think it has something to do with how wet this spring has been. Today was the first bit of blue sky we've seen in two weeks. Walking around today, my wife and I were very curious about the sequence of dandelions transition and the mechanisms by which these transformations take place. Here is a photo of some collecting we did today.


Our inquiry, the evolving stories we told, and the evidence we collected and coordinated with those stories made me wonder what kids would do if you drew attention to it, asked them what they thought, and helped them to wonder, collect evidence, and tell stories.

Light and Water: Post Ten

In this photo, you can see the water in an alpine pond acting as a mirror and a window, superimposed on each other. This phenomenon is fairly common in everyday life when looking at glass windows–depending how you focus your eyes, you can either see a reflection or see through the window. This is also true for laptop and TV screens, where you can often see both your reflection or what's on the screen. By focusing your gaze differently, you'll see one aspect more than the other.


This is cool is because, up until now, I have been focusing on factors mostly external to the viewer--the angle of light, the angle of the object, the wind, the particulates in the water, the intensity of light, etc. But here is where we can begin to think about properties of the eye, the camera, and the brain.

In the picture above, you can clearly see BOTH the mirror and the window behavior of the water. However, when I was standing there, I could "flip" my perception back and forth between seemingly just seeing the reflection and just seeing the bottom of the lake. The question is, "Is this something my brain is doing?" or "Is it something my eye is doing?" Is this a filtering process or a focusing process? Or is it a bit of both? My hunch is that it's more of an focusing phenomenon, because my eye actually gets tired trying to maintain certain foci, but I wouldn't be surprised if there were also a bit of my brain doing some selective-attentioning process.

Anyway, my goal is to find a similar situation and then manually adjust the focus in my camera to see if I can make a photo switch from mirror to window just by adjusting the focus, and not any of the external factors.

Light and Water: Post Nine

I went hiking today and couldn't help but take this photo of water acting like a mirror and a window.

In the picture, I am standing on a wooden platform looking down into a vernal pool. Where the sun shines directly onto the water, you mostly see all leaves at the bottom, but where I block the sun, you mostly see the reflection of the trees above.



In this photo, the wooden platform creates its own a shadow (as well as a shady tree to the left), and we see the same effect.

Light and Water: Post Eight

So far in my own inquiry into water and light, I've really been focused on understanding the role of viewing and illumination angles. Here are some ideas I'm more and more committed to:

• Shallow or glancing angles tend to reflect more off the surface of the water (like a mirror), This makes it so that being down by the lake you are more likely to see reflections, whereas being up high (looking down) on a lake you are less likely to see reflections. This relates to post two and post five
  
• A low sun behind you illuminates strongly the objects across the lake that are to be reflected, but the sun light only hits the lake with glancing blows (which mostly reflect away from you). The combination of strong illumination on the object and low levels back scatter from the sun make it easier to see the reflection.
  
• On the other hand, a high sun hits the water with more penetrating rays (not glancing), which refract into the water. In many cases, that light scatters off particles suspended in the water, which go off in all directions. In this case, the high amount of scattering creates noise that overwhelms any mirror reflections.
  

These last two bullets seem to concern post one and post seven

But there certainly is a role to be played by wind roughing the surface and the polarizing filter on my camera. So here are some photos that I think speak to this:

Here is an example I do think is likely wind, although glancing angles could still helping. This was also taken on Kidney Pond at Baxter State Park, looking toward Mt. OJI. I'm still doubtful that wind can fully account for this phenomena I posted about with the receding mirror boundary, but my mind is still open.


Here is one that I think has an effect from the polarizing lens (compare the real sky to the reflected sky). This photo was taken from the Stillwater River by the University of Maine.

I promise I'll get back to posting about teaching soon, but for now, I'm happily sharing my inquiry with you.

Light and Water: Post Six

This was picture was taken from Kidney Pond. Any guesses as to why I think this picture is interesting?

Light and Water: Post Five

In a series of posts, I have been sharing some of the fun and perplexing aspects of nature of light and water. In this post, I share some fairly contrived observations that seem to touch upon that perplexity in a new way.

For these photos, I took a blue marker and painted "a lake" on a small whiteboard. On my large whiteboard, I painted a blue face. Then I held the small white board up against big white board a a right angle (right by the face), and took some photos from various vantage points.

As you progress along the three photos, I change my viewing angle from glancing to more normal to the small whiteboard. What happens seems to be like what I showed you in post two, where the lake turned from a mirror to a sheet.

Some questions that I've been pondering over

1. How Can I explain the whiteboard phenomena
   
2. How might this be the same and/or different from water phenomena, especially post two?
3. Has this changed or refined my thinking about any of the previous posts?
4. In what ways is the whiteboard like a mirror and not like a mirror? And Why?

And for, fun, I added these photo as well.




And just to show you that this isn't a trick with markers



And lastly, a link to a movie

More natural and contrived observations are on the way.

Light and Water: Post Four

So far, I've been sharing photos that show bodies of water appearing as mirrors and appearing like sheets, depending on the conditions.

On twitter and in blog comments, I've heard about a range of ideas:

• wind roughing the surface of the water
  
• minerals, sediments, glacial flour in water influencing the color
  
• angle of the sun and the viewer changing what gets reflected to viewer, and
  
• those same angles changing whether the light mostly reflects off the water or refracts into the water.
• Update: The influence of a polarizing filter
  

In this post, I show three photos taken from Ship Harbor in Acadia National Park. In the first photo, the water acts like a window, letting us see into the bottom. With the second photo, I take few steps, turn my head, and the water changes character dramatically. How would you explain the difference? What, if anything, does this have to do with the ideas above and the phenomena shown in post one, post two, and post three.





In this third photo, the water shows its many different faces in a single shot.

Light and Water: Post Three

Here is post one. Here is post two.

In this post, I have a sequence of three pictures taken at Kidney Pond in Baxter State Park around the time the sun was setting. What, if anything, does this have to do with how we should be thinking about post one and post two?

Update: On twitter, the idea has been put forth by several that this is the result of the winds dying down as the sun goes down. The seeds of doubt for me is that it doesn't account for the receding nature of the boundary over time. I think it might have more to do with the portions of the lake receiving direct sun light. In other words the "image" of the trees is always there, but it's hidden in the noise of the scattered light. The image is "hidden" behind a curtain, and as we pull back the curtain, we see more and more of the image that was always there.

Light and Water: Post Two

In post one, I showed two photos of a glacial lake appearing quite different in the morning and the afternoon from the same location.

The two photos below were both taken in the morning. The first one was shot at 7:13 AM right on Lake Louise, and the second one was shot at 7:34 AM as I was little ways up the trail to the Beehive. Once again, we see the glacial lake appearing as a mirror and then appearing as an emerald sheet.

The questions now are: Why does the Lake look different in these two photos? How does this explanation compare to your explanation for post one?

Light and Water: Post One

The two pictures below are from Banff National Park. Every morning, the glacial lakes began as mirrors, but by afternoon those same lakes would turn emerald. The question is why?

One Situation: Multiple Force Models

I like this picture. And one reason I like it is because it reminds me that there is no correct way to a model a situation using a free-body diagram. Here are four free-body diagrams.







While the models becomes more sophisticated; I don't think any of these models is correct or incorrect. Depending on its purpose, sometimes the simplest model is the best one. All of this makes me wonder what dis-service we do to students when we over-emphasize the correctness of a free-body diagram and under-emphasize the fact that we are building and refining models. As we come to notice and become concerned about more nuanced features of a situation, we may (or may not) choose to attend to those features.

Snow Column Buckling

We got a really wet snow storm yesterday, allowing the snow to stick to the side of the wood on my balcony. In the morning, as it started to get warm, several of the columns started to buckle like this.


I thought it was cool enough to share. Doesn't the big kink look unstable? Oh yeah. I took this picture, turned away for a second; by the time I looked back, the column had collapsed.


Here's another baby one:





What physics do you see here? What does this picture make you wonder about?

What could you do with this?

Here are photos of the sunrise taken from my balcony. One is from August. The other is from January. What question could I ask students? What questions could my students ask? What could I ask them to do with this?