Today in my inquiry class we did three things:
First, I gave a 10-15 minute “lecture” on their collective ideas about light that have come up over the past two weeks. I did my best to summarize, represent, discuss, and provide arguments and evidence for the range of ideas I’ve heard in class. I reviewed our very early ideas about light (that many of us have since decided to abandon) such as light coming out of a flashlight like a “cartoon beam” and how light can “leak” or “spill over” off its path. I reviewed our initial observations and how those observations were different than what we had expected based on our initial predictions. Next, I elaborated upon and defended several competing ideas about the nature of light:
The idea that you’d be able to see a beam going by if you could just get a strong enough concentrated beam in a really dark area.
The idea that you can only see a beam of light when it passes through something like dust, smoke, fog, etc.
The idea that there is no such thing as a beam; rather you just see the objects in the path of light–be them dust or droplets of moisture.
I elaborated on two prevailing ideas about why we see objects like dust in the path of light: one being that the dust absorbs light, thereby making them visible; and another that light bounces of it in all directions.
I also reminded them of several of the collective observations we had made during our at home observations, including observations that led to a better articulation about the conditions under which a beam does and doesn’t seem to appear; a better articulation of what observers see standing and looking in different directions relative to flashlight; and a better articulation of the shape and brightness of lit areas from a flashlight across different distances.
Second, I asked them to discuss with their research group, the questions and puzzles they had and to note which ones they’d be interested in pursuing. Here is the list they generated:
Reflections and Absorption Questions
What is the nature of reflection? Scattering? Kooshing? Bouncing? Bending?
Is light absorbed into an object or reflected off an object, or both?
Does material make a difference in the amount of reflection?
How do glow in the dark stickers work? Do they need light to glow? Would heating work?
If light absorbs (soaks) into objects like dust or water (making them lit), why don’t water droplets stay lit when the light is turned off?
Does photosynthesis and solar panels work by trapping and holding light or absorbing it?
Can a beam be present even if we cannot see it with our eyes?
Does their have to be something like moisture in air to see a beam? Why does dust matter?
Does flashlight on a wall show a circle because of the mirror in the flashlight or circle shape of the flashlight? What effect does different shaped flashlights have?
What causes the bulls-eye effect? What causes changes to the bulls-eye effect? Why is there sometimes a dark center vs. bright center?
What does the mirror really do in the flashlight?
What doe the adjustor on the flashlight do?
Other Light Questions
Why does light get dimmer over distance?
Does light travel straight or does it expand to get bigger?
What is difference between light from sun and light from something like a flashlight?
What is UV light?
What effect does the color have on light?
Is energy being transferred from particle to particle as light moves?
Is light energy? How does light energy turn into heat energy?
Third, students set out to begin deciding what questions or puzzles they were interested in pursuing, and then they investigated, discussed, and wrote in their notebooks for a little under two hours.
Several groups investigated how light “reflects” off different surfaces–some looked at white, black, and mirrored surfaces, others looked at “glossy” vs “matte”; others used different colored construction paper. Some looked more at where light went and others looked at more the brightness of the color of the light. Some groups even ended up looking at the transmitted light. The fact that we have several groups doing this with slight variations is nice, and will hopefully make contact with some of the other groups’ more complicated inquiries where they made interesting discoveries that they are struggling to explain.
One group investigated the puzzle of why there is sometimes a black spot in the middle of flashlights. They found that both the distance from the surface matters and the “focus” of the maglite matters. They ended up redoing their maglite dissections and then playing with the mirrors to see how moving the mirror around changes how the light gets focused. This group is feeling a little overwhelmed with the complexity of it all. I think they might have thought it would have been a simple, “OK, let’s just go look, take some measurements and that will be it.” Instead, the complexity of the dark spot unraveled quickly.
Another group got wrapped up in the why shining a flashlight on a whiteboard led to them seeing TWO spots of light– for one spot we could all agree where to point on the whiteboard, but the other we had a hard time showing others where we saw it to be. They also found that a regular old wood door does the same thing, even though it’s not as glossy as the whiteboard. They are intrigued, perplexed, and pretty excited I think.
Another group investigated how different colors and strength of flashlights lead to absorption, which they surmised would lead to heat. They also found that strong lights made the color fade (or change) on construction paper. I honestly don’t know why the colors fade. My instinct is see if this group will go off in a different direction, but I’m going to be careful and wait to see where they go with some careful listening and questioning.
One other group recreated our initial hallway experiment with different kinds of walls; black walls, white walls, and found that the curved boundary between dark and light was not as distinct with white walls as it was with the black walls. They have some ideas about how they might explain it, but I’m having hard time pressing them to make some drawings to show exactly how they think the light gets from the source to the walls to wherever its going next.
Sorry for the long post… I’m still kind using this blog as a teaching journal at times…
You seem to denigrate the use of a blog as a teaching journal at the end there. Perhaps this has been debated elsewhere and I am oblivious, but I see no need to apologize. This is fabulous stuff.
I am particularly struck by your defense of these introductory notions of light. Modeling this is so, so important for developing critical thinking in students. It takes some skill to summarize these ideas so well and to describe them meaningfully while still leaving open the important questions you want your students to consider.
And those questions they’re working on? Holy cow! Those are amazing. I would consider myself more knowledgeable than the average citizen on this topic (but not knowledgeable enough to pass a physics final), and I’m curious about some those questions. Lovely, lovely stuff. Best wishes to you and your students in your quest for the meaning of light.
Thanks Chris. I didn’t mean to poo-poo the teaching journal /blog. I just got to the end and felt, “Man, I just wrote a lot. Does this need an edit before I submit? Nah, I’ll just apologize for the ramble.” I love that my blog serves multiple functions–one of them being a place to reflect and document my thinking about my teaching and my students’ learning.
I debated a bit about whether to give this lecture, but decided to got for it–to model for them explicitly what it means to listen (not only to an idea), but to listen across ideas and for their development over time. I’m also interested in these questions and in their inquiries, so it keeps me excited with them.
Glad you’re using your blog as a teaching journal, Brian. I’ve jumped into a somewhat similar process, but without a clear idea of how to carry it off! Reading your description of your “decision-tree” helps me see new options and weigh them.