How do you teach what polarization is?

Today is Optics Day at CREOL, our annual public open house where we present demonstrations of various optical phenomena and technologies, speakers, and pizza. :)

During this year's Optics Day I am charged with explaining the phenomenon of polarization to visitors. Now, I find polarization incredibly difficult to explain to non-scientists, and here's why: the usual treatment of optical polarization in physics involves describing the direction of the electric field vector of an electromagnetic wave. If I were to start with this definition while speaking with somebody not trained in physics, I would then have to explain electromagnetic waves. This would be followed by an explanation of the equivalence of light and electromagnetic waves, wave phenomena in general, linear, circular and the more general elliptical polarization states, etc. etc. until the poor person who has come to see a cool demonstration and learn something new has completely been befuddled because it takes so much background understanding to comprehend what polarization even means.

This year, I am determined to find an explanation of polarization that is more intuitive to a non-scientist. A rough outline that I intend to give for polarization's foundation in observation goes as follows:

1) Our sense of sight is perhaps the most obvious sense we have. We see objects and from these objects we discern shape, size, color and other properties.

2) There are physical quantities that cannot be sensed by our eyes. For example, flowers have fragrance that our noses can detect. Wind is another example. We feel its effects or we see its effects on other things, but we don't directly see "wind." Therefore, there are physical quantities that cannot be seen but nevertheless may be sensed.

3) There are still more phenomena that exist but cannot be sensed by any of our sense organs. For example, a compass points north because the needle experiences a magnetic force. Additionally, small objects all fall towards the earth because of gravity. Magnetism and gravity require tools that sense things that we cannot: magnetic and gravitational fields. Where our senses fail us, we use tools to measure some quantity.

4) Polarization lies in this last classification of phenomena. It cannot be sensed by us (which isn't strictly true), but can be determined by appropriate tools. These tools are things that are found in nature, like quartz crystals, and man-made objects like polarizers and waveplates.

From this foundation, I will explain some of the consequences of the polarization of light, what it can be used for, and may even digress into the physicist's model if the visitors are interested enough. My hope is to build the concept of polarization up from a basis of observation, not to start with our model first, followed later by how we observe polarization.

A primary school method for multiplication of numbers

I found this link that was posted by a friend on Facebook this morning. It's a pictorial description of an algorithm for computing the multiplication of two-digit numbers. I haven't had time yet to think about it, but so far as I can see now it's useful only for computing the product of numbers with one or two digits. Still, it's pretty cool.

In 2011 I had a calendar in my office on mental math algorithms called Lightning Calculation, which I believe I also mentioned in an earlier post. Check this out if you wish to train your brain in the powers of mental computation!

So I've been busy...

Yes, I realize that I missed a regular post day. However, I've been home drinking lots of coffee and beer and eating creamed cabbage, creamed potatoes, creamed, well, everything. So, I humbly apologize that my thoughts have shifted to gastronomy this week. I should mention that I will also likely miss next week's post as well.

In the meantime, since I have been thinking much about food, I direct your attention to the Maillard reaction, one of the most important chemical reactions in cooking! If you like toast, roasted vegetables, or browned steaks (I'm vegetarian, but fondly remember this part of my past), you have this non-enzymatic reaction to thank.

Happy holidays!

The best abstract ever?

By way of my advisor, concerning the recently found anomaly in the neutrino speed measurement at CERN:

http://arxiv.org/abs/1110.2832.

As far as abstracts go, it does succinctly summarize their findings ;)

No deep insights for today

Well, I just returned from a great wedding in Columbus this past weekend (no, not my own), which means I've been incredibly busy catching up at school... again. I wanted to write a post on curve fitting since I've been involved with the task in my data analysis lately, but I just haven't had the time to flesh out a coherent post.

So instead, I leave you with the URL of a cool new website from Ben Goldacre: http://nerdydaytrips.com/. The site is a user-fed collection of short day trips that might appeal to the more—ahem—academic of us. There seems to be a nice garden near me in Lake Wales, FL called Bok Tower. Perhaps if I can get a free weekend I'll pay it a visit.

And did anyone see the Buckeyes game last Saturday? I think we have a future with Braxton Miller.

Random thought on random walks

I've been working a lot lately with both models and experiments concerning Brownian motion of microparticles in suspension and had a plot of particle trajectories that underwent a 2D random walk up on my computer screen. My officemate commented that it looked like the scribbles that her niece does with crayons and it got me thinking: can the scribble trajectories of children be modeled as some sort of random walk? I imagine it'll likely be anisotropic since they seem to scribble either primarily up-and-down or left-and-right. But it would be an interesting sociological study to try and correlate the statistics of the scribbles (fractal dimension, diffusion coefficient, etc.) with some societal factor.

Yes, this would likely be frivolous science but I'd find it fun anyway =)

The coffee-spilling uncertainty principle

If, when carrying your cup of coffee back from the coffee machine to your office, you hold the full cup close to you, you're less likely to spill any over the sides of the cup, but if you do spill, it is more likely to spill on your clothes. However, if you hold it further out from you, the coffee is much more likely to spill over the side of the cup, but much less likely to spill on your clothes.

The uncertainty in spilling your coffee multiplied by the uncertainty in spilling your coffee on you is always greater than Planck's constant times the amount of time spent at work.

Science and cooking online

Those who know me are aware that I am a big science buff. Those who know me even better know that I also am an avid cook and baker.

Harvard gave a lecture series this past fall on science and cooking and have graciously posted the lectures online. I recommend taking a look here.

Topics include thermodynamics, colloids, and sous vide cooking.

Mentat training

For Christmas I received a "Lightning Calculation" calendar. It's a wall calendar that explains techniques for performing mental calculations, such as finding what day of the week a date fell on and performing fast multiplications. In addition, there are historical bits on famous individuals who have been able to perform incredibly complicated mental calculations. I've spent at least half an hour in my office every morning reading through it and trying the practice problems (of which there are hundreds, if not over a thousand).

Something I've learned is the anchor method for multiplication of two, two-digit numbers. It may seem complicated at first, but it's actually incredibly powerful. First consider the product to be found as a product of two sums, each one "anchored" to a nearby round number. This product can be written as

(a + c)(a + d) = a^2 + ac + ad + cd
(a + c)(a + d) = a(a + c + d) + cd

where a is the anchor. From the right-hand-side of the last line above, the anchor is multiplied by itself with the sum or difference terms c and d. Then the correction term cd is added or subtracted, depending on whether the signs of c and d were the same or not, respectively.

For example, consider the product 17 * 18. This can be written as (20 - 3) * (20 - 2) = 20(20 - 3 - 2) + (2 * 3) = 306. The algorithm is easy to carry out because the first product is 20 * 15 = 300. Cool stuff.

The information for the calendar can be found here: http://myreckonings.com/wordpress/2010/11/22/a-2011-%E2%80%9Clightning-calculation%E2%80%9D-calendar/. It's very nicely done and I highly recommend it for all those mentats in training =)

Osmotic fun

In my readings on how to properly maintain cell cultures underneath a microscope, I came across the entry for osmotic pressure on Wikipedia. In the introduction, a thought experiment is described as such:

In order to visualize this effect, imagine a U shaped clear tube with equal amounts of water on each side, separated by a membrane at its base that is impermeable to the sugar molecules (made from dialysis tubing). Sugar has been added to the water on one side. The height of the water on each side will change proportional to the pressure of the solutions.

Just like my post on a proposed experiment dealing with entropic elasticity in rubber bands, this looks like an interesting and easy demonstration to perform. That is, if I have time to devise the setup (I'm also still working on the entropic elasticity experiment and a demonstration of Schlieren photography for CREOL's student group's outreach program, CAOS).

Fun with thermodynamics

Admittedly, the thought experiment I'm about to tell you about is simply explained by thermodynamics. Despite this, I puzzled over it for a while since it is very counter-intuitive, at least to me.

Suspend a weight from an elastic band so it is stretched (only slightly) beyond its equilibrium point. Now, heat the band with a hair dryer. Does the weight move up or down?

Give up? It moves upward. Do you know why?

I plan to verify this experimentally at some point.