Tag Archives: refraction

Walt Disney World’s IllumiNations at Epcot

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For Spring Break I travelled with a few of my friends to the happiest place on earth where the days were beautiful and sunny and the nights were clear and mild. On Wednesday night we travelled to Epcot and stayed late enough to see the IllumiNations: Reflections of Earth fireworks show. For those of you who have not had the pleasure of visiting Epcot, the park is a circle comprised of different countries and in the center is a huge lake. This is where IllumiNations is held and throngs of people crowd around the “world” to watch the magic begin over the water. The sun was finally setting and the last rays of light danced across the water. I’ve seen a number of sunsets before but this was the first time I was able to break down what was really happening with the light, the way it traveled through my eye and how I was still able to see the light show in the dark.

Let’s begin with the sunset and how the light from the sun traveled into my eye. Here’s a picture of what it looked like:

sunset

We learned in class that when the sunlight is traveling through the atmosphere some rays are absorbed by particles while others are scattered in different directions. Next, the light that has made it through the atmosphere will either be absorbed or reflected when it hits the surface of an object. I had time before the sun went down to snap a picture of Rafiki and Simba to show you what I mean. The colors that you see have been reflected while the colors you don’t see have been absorbed. For example, let’s take a closer look at Rafiki’s light blue cheeks. We see light blue because that color blue on the electromagnetic spectrum has been reflected into our eye while the other wavelengths like red, yellow, green, etc. have been absorbed.

lionkingflowers       rafiki cheek

The light that is reflected from Rafiki’s light blue cheeks first makes contact with the cornea of our eye. The cornea is a clear surface at the front of the eye so most of the light is transmitted through it into the eye. The cornea is the primary refractive surface of the eye and has 80% of the focusing power, which means the cornea is able to bend the light in such a way that the picture becomes a clear image on the retina. Once the light reaches the retina it will strike photoreceptors, which will basically absorb the light, which leads neurons in the retina to fire action potentials all the way up to the brain. The retina transduces, or serves as a translator that receives the light and sends the “message” up to the brain in a language that the brain can read and understand. Thus we are able to clearly focus and recognize the world around us!

The light of day was quickly disappearing and the light show was about to begin. The entire park went dark except for an illuminated globe that was floating across the water. We learned in class that we are able to see glow-in-the-dark objects because they become our new light source. You can see what I mean from the picture below.

illumi

IllumiNations was a great show and the fireworks were fantastic! I have a new found appreciation for the world around me now that I know the process that goes into letting me see.

fireworks

Works Cited

“Sensation & Perception: Home.” Sensation & Perception: Home. N.p., n.d. Web. 17 Mar. 2014. <http://sites.sinauer.com/wolfe3e/home/startF.htm>.

Myopia at a Mets Game

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When I was nine years old my father took me to my first New York Mets game at Shea Stadium and I was thrilled to watch my favorite baseball team play live. However, upon taking our seats way up in the stands during the first inning, I realized that there would be a major problem for the remainder of the game. As I looked hundreds of feet down to the field, everything was blurry- I couldn’t see David Wright’s number on his jersey; I couldn’t see the numbers on the scoreboard; I couldn’t even see where the ball was being thrown. This angered me because I could read the scorecard in front of my face just fine, but everything went from clear to blurry as the distance from myself increased.

Consequently, I took a trip to visit my eye doctor the following day. I informed Dr. Rubin of the difficulty I was faced with during the previous day’s activities and he asked me to sit in a chair so he can perform some tests. One specific evaluation that I remember was when Dr. Rubin placed a series of random letters in front of me that decreased in size with each progressive row. “Read aloud all the letters in row four,” he said. In response I called out, “E, H, F, B …” and so on. Next came row five and the same process was repeated. Finally when Dr. Rubin asked me to announce the letters in row six, it became obvious that my vision was blurry- I’m not sure if I was correct on even half of the letters that I shouted. At the end of my visit, Dr. Rubin said, “Okay Dylan, that’s all. It turns out that you have 20/30 vision and will need to wear glasses when looking at things far away because you’re near-sighted.” I had no clue what most of this meant at age nine, but I knew that I had dreaded the idea of having to use glasses in class, in the movies, and in any other public place.

What I didn’t realize at the time, was that those glasses that Dr. Rubin prescribed were very important for me to function properly. Apparently, I had vision that was considerably worse than the average person; the fact that my vision was 20/30 meant that I had to be at 20 feet to read the same letters that someone with normal vision could read at 30 feet. The test of decreasing letter sizes that Dr. Rubin used to determine this visual acuity, or the smallest spatial detail that I could resolve, happened to be the same that all eye doctors used. Additionally, the fact that I was considered “near-sighted” meant that I had myopia. To understand myopia, one must first know how light rays are focused in the eye.

First off, every person has a lens system that is responsible for refracting, or bending, light from many different angles onto the same point of the retina- the layer of neurons in the back of the eye. Although this system creates a bright image for a person to perceive things better, it can sometimes make that image appear out of focus. The cause of this problem is called accommodation, which is when the lens changes its original shape and thus alters its refractive power. The improper refracting from this accommodation in my particular lens system resulted in myopia. Since my eyeball was too long, the point of focus for that bending light fell in front of my retina, rather than on it. This is why Wright’s number appeared burry, while the scorecard appeared clear at the baseball game when I was nine years old. It’s a shame that the light that entered my eye couldn’t have been bended appropriately onto my retina, with no refractive error. Unfortunately, I was not lucky enough to have such emmetropia, as experts call it, and instead was stuck with myopia and those horrible glasses.

Despite my initial embarrassment about wearing glasses, in time I came to truly appreciate those helpful lenses because I was finally able to see things properly. Those negative lenses were able to diverge rays of light before they entered my eye and thus corrected my myopia issues. As a result, I was able to happily watch my favorite team play the next time I attended Shea Stadium for a Mets game and didn’t have to worry about anything being too blurry to see.