|Kayaking with kids|
|Teaching kids how to fish|
We caught an assortment of sea life throughout the week at Piers Park. I started out the week catching a spider crab, which kinda looks like a rock with long legs (it looked more like a rock than the rock crab we caught, interestingly enough). On Tuesday we caught a lobster, which up until then I didn't know lobsters could be caught on fishing hooks, but empirical evidence has proven me wrong. The lobster was a keeper, meaning that it was between a minimum and maximum length (these limits are in place to try to make sure lobsters don't go extinct. Young and old lobsters get to live, basically.) Michael let the lobster go after the kids played with it because it was a female lobster and would eventually give birth to more lobsters. Some other animals we caught were rock gunnel, perch, green crabs, a starfish, and minnows.
One of my favorite activities this week was teaching kids about refractometers. I'll explain in further detail how refractometers work below but for the kids I gave them a brief lesson on what salinity is and how to read a refractometer. I explained (in simpler terms than I use in this blog) that the number they read on the refractometer corresponds to the amount of salt in the water in a unit called parts per thousand (n molecules of salt in 1000 molecules of water, where n is the value on the refractometer). In order to fully explain refractometers we'll have to go over how refraction works, and how different substances have different values on the refractive index. Basically, the higher the difference in refractive index values two substances have, the more light bends when crossing the border between those substances. It's why objects in water appear closer than they actually are: water has a higher value on the refractive index than water, so light bends towards the observer when crossing the water-air border. The other concept refractometers use is a phenomenon called internal reflection. Internal reflection occurs when light hits the border between substances of differing refractive index values on the side of the higher refractive index value. At an angle called the critical angle, or any angle with a lesser value than the critical angle, light bounces off of the border rather than passing through and refracting. Now that we've gone over refractive indices and internal reflection, we can get back to refractometers. Refractometers bounce and refract light in such a way that slight differences in water samples, like salinity, will refract water and change the angle that the light is approaching to an angle less then the critical angle, creating internal reflection. This is what creates the different areas in the lens of the refractometer: the blue and white areas that, when you look at the border between them, give you a numerical value for the salinity of the sample in ppt.
|Visual representation of refraction|
Song of the week: La Di Da by The Internet
See you in the next blog!