We are just beginning our unit on electricity, today was day one. Stemming from New Latin, electricity means “amber-like,” because some really old guys put it together that rubbing amber on fur would result in the attraction of very light objects such as feathers. They had way too much time on their hands. To kick off our new little unit, Mr. Wirth aka “Dubbs,” began by performing the following demos: rubber and fur, glass and silk, rotating rod, magic water, and the electroscope. The electroscope is used to detect the magnitude of electric charge on a body. A gold leaf electroscope is pictured below:

Notice that the two gold leaves separate from each other, indicating the presence of an electric charge. If the electroscope is brought near a charged object, without touching it, the leaves diverge, because charges in the disk with identical polarity to the charged object are repelled to the leaves. A pretty complicated way to tell that something is electrically charged, but it gets the job done. Next up is static electricity. It is not really static because electrons have obviously moved around, but in any case the electrons stick to objects that are poor conductors of electricity. This phenomenon of static electricity requires a sustained separation of positive and negative charges; when you touch the surface that is charged, you get a pretty sick shock. Ever shocked someone on their neck with your finger? That’s pretty much static electricity right there. This is quite possibly the most messed up picture I have ever seen, but it shows what’s up with static electricity. Don’t let this be you:

The fundamental idea behind electricity is matter, and the fact that it is composed of atoms. In turn, atoms are composed of protons, electrons, and neutrons. Protons have a positive charge, electrons have a negative charge, and as you may be able to guess neutrons are neutral. Certain objects can and do become electrically positive or negative when they have a lack or an excess of electrons. Why electrons and not protons? Protons are constant; they are trapped in the nucleus of the atom and cannot get out. When an object has an equal number of protons and electrons, it is electrically neutral. We have here students a picture of an atom:

By loosing or gaining electrons, metals become positively or negatively charged. For the rest of the class we watched a short video. Peace-PC

The Human Eye

Taryn McCrobie
The Human Eye
The eye is an essential organ within the human body. Without it, our days would be dark and gloomy. We wouldn’t be able to witness the wonders of a rainbow or the magic of a starry night. Although we constantly use our eyes, most people do not know very much about them. Therefore, by researching the anatomy, function, and problems of the eyes, I was able to not only expand my knowledge, but will now also be able to take better care of my eyes.
The eye is a very unique and important organ within the human body and it contains three layers of tissue to allow it to do its job. The first of these layers is called the sclerotic coat (sclera). This is a tough layer which appears white everywhere except the cornea. The cornea is a raised area on the front of the eye which admits light and bends the light rays so that a single image can be made. In order to perform its essential function, the cornea is kept moist and clean by the secretions of the tear ducts in each eye. This is made possible by the conjunctiva which is a mucus membrane on the inside of the eyelids. When an infection occurs in this area, it is called conjunctivitis, more commonly known as pink eye (Basic).
The second layer of light is called the choroids coat and is extremely pigmented with melanin. The major job of this layer is to reduce the reflection of light within the eye so that a more focused image may be produced. It also contains the blood vessels that supply blood to all of the structures of the eye. The choroids coat on the front of the eye is called the iris and is forms the color of the eye depending on how much melanin there is. Less melanin makes blue eyes while more makes brown. The ciliary body is also a part of the second layer of the eye. This is a muscular area that is attached to the lens to control the amount of light that enters the eye by regulating the size of the lens. The dilator is the muscle that allows the iris to become smaller which makes the pupil larger to allow more light to come in. This is good for human vision at night because each shred of light that can be reflected into our eye allows us to see our dim environment better. There is also the sphincter which makes the iris larger and the pupil smaller to allow less light within the eye. This is helpful in broad daylight when there is more than enough light to see things around us and too much of it could damage our eyes (Basic).
Finally, the last layer of the eye is the retina. This contains cones and rods which are the light-sensing portion of the eye. Rods are used for vision in low light while cones are used for color vision and detail. In the center of the retina is the macula and in the center of that is the fovea centralis, an area which contains only cone cells and is responsible for seeing the details of the environment around us. The retina is also made up of a chemical called rhodopsin called “visual purple” that converts light into electrical impulses that the brain deciphers into vision. To do this, there are also the retinal nerve fibers at the back of the eye which form the optic nerve. The optic nerve then conducts the electrical impulses to the brain. However, there is one section within the eye where the optic nerve and the blood vessels exit the retina. This spot is called the optic disk and results in a blind spot because of the lack of rods and cones. Lucky, each eye covers the other eyes blind spot so no grief comes of it. The optic disk is represented in the picture to the right (Basic).
Within the eyeball are two chambers full of fluid and separated by the lens. The larger of these contains a clear gel called the vitreous humor. The second chamber contains aqueous humor which is also clear but very watery fluid. This section is split up into two parts called the anterior chamber and the posterior chamber. The liquid is produced in the ciliary body and is drained through the canal of Schlemm (Basic).
The eye also contains a lens which is shaped as a bi-convex structure and is about 10mm in diameter. The lens is able to change shape because it is attached to muscles around the eye. This part is essential for fine-tune vision (Basic).
Since it is so delicate, the eyeball is protected within the orbital cavity which is made of bone. Within the bone, the eye is in a layer of fat which is similar to resting on a pillow. The eyelids protect the open portion of the eye from dust by blinking away dust and dirt in the air. This also keeps the eyes moist by spreading the liquid from the tear ducts. Tears are produced through lacrimal glands which are located above the outer segment of each eye and then drain down into the inner corners of each eye. Finally, eyelashes and eyebrows protect the eyes from larger particles that may result in injury. However, the eyeball is still able to move around because the orbital cavity is round and the fat is flexible. The muscles that allow this movement may be seen in the picture above (Basic).
In order to see color, various color-responsive chemicals in the cones are used called cone pigments. It is very similar to the mechanics of the rods except photopsins are used instead of scotopsin. This leaves the pigments to be made of retinal and photopsins and creates three kinds of color-sensitive pigments. These include red-sensitive pigment, green-sensitive pigment, and blue-sensitive pigment. Each cone cell has one of these pigments and can therefore only sense one of these colors. In addition, the eye is able to see almost any color that results from a mix of one of the three pigment colors. The diagram to the right shows the wavelengths of the three types of cones at the colors peak absorbency (Color Vision).
However, since the eye is such a complex organ, it can have numerous problems. One such problem is color blindness. Color blindness can be defined as “the inability to differentiate between different colors.” This problem is more common among males (eight percent of males are color blind) than females (four percent of females are color blind). The most common type of color blindness is with red-green and occurs when either the red of green cones are not present or not performing as they should. Fortunately, people with this problem, are still able to somewhat see these two colors, however, they often mix them up. This is a genetic disorder that is carried on the X chromosome and is very rare in seeing only different shades of gray (Color Blindness).
Another very serious problem is blindness. Normal vision (or visual acuity) is determined by reading a Snellen eye chart (to the left) and can be defined as 20/20 (being able to see an average amount of details from twenty feet away. 20/40 vision represents bad vision in that while you stand twenty feet away from something, you are only able to see what a normal person can see at forty feet. This logic continues up to 20/100 and at 20/200, one reaches the cutoff for legal blindness in the United States (Normal Vision). There are various ways that a person can become blind. A common one of these are cataracts which is cloudiness in the lens that blocks light from reaching the retina. Luckily, this may be cured through surgery by removing the lens and replacing it with an intraocular lens. Another way that a person may become blind is through glaucoma. This occurs when the aqueous humor fails to drain correctly and pressure builds up in the eye. This causes the cells and nerve fibers in the back of the eye to die. However, this may also be treated with medication and surgery. Diabetic retinopathy can also cause blindness and is the result of diabetes. A person with diabetes can easily get a blockage or leakage of blood vessels which can lead to scarring and ultimately, blindness. This may be treated with laser surgery. Trachoma is an infection that is caused by an organism called Chlamydia trachomatis which often causes blindness. However, it is very rare in the United States because it can easily be treated with antibiotics (Blindness).
Another common problem of the eye is nearsightedness and farsightedness. Nearsightedness (shown at the right) occurs when a person can only clearly see objects that are close by. Objects that are farther away are brought into focus at a point in front of the retina which makes them appear fuzzy. However, a diverging lens can be placed in front of the eye to adjust the light rays so that the image rests on the retina, creating a focused image. Farsightedness on the other hand can only clearly see objects that are farther away. Close objects are focused at a point behind the retina which also creates a fuzzy image. A converging lens can be used to cure this, however, by allowing images to once again, rests directly on the retina. Farsightedness can be show in the picture below (Sight).
A less common problem that occurs within the eye is Vitamin A deficiency. As a result of extreme deficiency, night blindness may occur. Vitamin A is necessary for retinal which is part of the rhodopsin molecule within rods. When there is a lack of Vitamin A, the levels of light-sensitive molecules become low. With this, the low amount of light may not be able to be detected by the weakened eyes. However, during the day, there is enough light for vision even if there is a low amount of Vitamin A (Vitamin A).
We all know that the eye plays an essential role in our every day activities. However, many people don’t know how complex the eye can be, and how many problems it may obtain. By learning more about it, we may be able to prevent getting these various problems in the future.


Works Cited

Bianco, Dr. Carl. "Basic Anatomy." How Vision Works. How Stuff Works. 3 Mar 2008

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Bianco, Dr. Carl. "Blindness." How Vision Works. How Stuff Works. 3 Mar 2008

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Bianco, Dr. Carl. "Color Vision." How Vision Works. How Stuff Works. 3 Mar 2008

.

Bianco, Dr. Carl. "Color Blindness." How Vision Works. How Stuff Works. 3 Mar 2008

.

Bianco, Dr. Carl. "Normal Vision." How Vision Works. How Stuff Works. 3 Mar 2008

.

Bianco, Dr. Carl. "Vitamin A Deficiency." How Vision Works. How Stuff Works. 3 Mar

2008 .

Sight. Think Quest Junior. 3 Mar 2008

.

Human Eye

The human eye is unique in that it accommodates for different light intensities and also focuses light rays that come from different distances from the eye. Light is then converted into impulses and sent to the brain where this image is perceived as what it looks like. Vision is very dependent on light. The light rays are reflected off object and then make their way into the eye. The light rays enter the eye through the cornea and the cornea refracts the light as it enters the eye. After passing through the cornea the light rays pass through the opening called the pupil. The iris is the part of the eye that controls the dilation of the pupil. This allows a certain amount of light into the eye.

How we see colors- The retina has cells called rods and cones. The rods and cones absorb light rays and change them into electrical signals. The electrical signals are then transmitted to the brain, which produces the familiar sensations of color. If any part of this system is damaged, then people may lose their ability to see some or all colors.

Color Blindness- The inability to perceive differences between some or all colors Two main types of colorblindness: Red/Green Blue/Yellow

Causes- Often due to genetics Also can result from damage to certain areas of the body… Eye, Nerves, Brain, Exposure to certain chemicals

Signs/Symptoms- Difficulty distinguishing between reds and greens Difficulty distinguishing blues and greens Objects appearing as various shades of gray Reduced vision Nystagmus-involuntary eye movement

Diagnosis- Most commonly detected with Ishihara Test Plates Ishihara Test Plates-Special colored charts that are composed of colored dots that form the shape of a number If the patient can not distinguish between certain colors then they will not be able to detect the number on the chart.

Treatment- No known treatment People with colorblindness learn to associate certain colors with objects to better identify colors. This helps in determining and recognizing certain colors.

Statistics- The most common form of color blindness is Red/Green Color Blindness Consists of 99% of Color Blindness cases Blue/Yellow color blindness is rare Total color blindness is extremely rare

Rainbows

Rainbows are optical and meteorological phenomena that have amazed people for as long as time. The beautiful colors that appear in a rainbow (red, orange, yellow, green, blue, indigo, violet) all make for an exquisite sight to see.
The “bow” part of the word describes the fact that the rainbow is a group of nearly circular arcs of color all having a common center. Though rainbows are bow-shaped in most cases, there are also phenomena of rainbow-colored strips in the sky: in the shape of stripes, circles or even flames. So it is not always a rain”bow!”
Rainbows cause a spectrum of light to appear in the sky when the Sun shines onto droplets of moisture in the Earth's atmosphere. The traditional rainbow is sunlight spread out into its spectrum of colors and diverted to the eye of the observer by water droplets. The rainbow's appearance is caused by dispersion of sunlight as it goes through raindrops. The light is first refracted as it enters the surface of the raindrop, reflected off the back of the drop, and again refracted as it leaves the drop. The overall effect is that the incoming light is reflected back over a wide range of angles, with the most concentrated light at an angle of 40°–42°. A color that travels more slowly in glass will bend more sharply when it passes from air to glass, because the speed difference is more severe. A color that moves more quickly in glass won't slow down as much, so it will bend less sharply. In this way, the colors that make up white light are separated according to frequency when they pass through glass. If the glass bends the light twice, as in a prism, you can see the separated colors more easily. This is called dispersion. Drops of rainwater can refract and disperse light in the same basic way as a prism. In the right conditions, this refraction forms rainbows.

Rainbows are optical and meteorological phenomena that have amazed people for as long as time. The beautiful colors that appear in a rainbow (red, orange, yellow, green, blue, indigo, violet) all make for an exquisite sight to see.
The “bow” part of the word describes the fact that the rainbow is a group of nearly circular arcs of color all having a common center. Though rainbows are bow-shaped in most cases, there are also phenomena of rainbow-colored strips in the sky: in the shape of stripes, circles or even flames. So it is not always a rain”bow!”
Rainbows cause a spectrum of light to appear in the sky when the Sun shines onto droplets of moisture in the Earth's atmosphere. The traditional rainbow is sunlight spread out into its spectrum of colors and diverted to the eye of the observer by water droplets. The rainbow's appearance is caused by dispersion of sunlight as it goes through raindrops. The light is first refracted as it enters the surface of the raindrop, reflected off the back of the drop, and again refracted as it leaves the drop. The overall effect is that the incoming light is reflected back over a wide range of angles, with the most concentrated light at an angle of 40°–42°. A color that travels more slowly in glass will bend more sharply when it passes from air to glass, because the speed difference is more severe. A color that moves more quickly in glass won't slow down as much, so it will bend less sharply. In this way, the colors that make up white light are separated according to frequency when they pass through glass. If the glass bends the light twice, as in a prism, you can see the separated colors more easily. This is called dispersion. Drops of rainwater can refract and disperse light in the same basic way as a prism. In the right conditions, this refraction forms rainbows.
A rainbow does not actually exist at a particular location in the sky. It is an optical illusion whose apparent position depends on the observer's location and the position of the sun. All raindrops refract and reflect the sunlight in the same way, but only the light from some raindrops reaches the observer's eye. This light is what constitutes the rainbow for that observer. The position of a rainbow in the sky is always in the opposite direction of the Sun with respect to the observer, and the interior is always slightly brighter than the exterior.
Rainbows are amazing marvels that are the result of hard science at work!

Works Cited
http://www.atoptics.co.uk/bows.htm
http://eo.ucar.edu/rainbows/
http://www.jiskha.com/science/earth/rainbows.html

Rainbows, Mirages and the Sky

Physics is a huge part of our life that we are oftentimes unaware of. For example, people all around the world appreciate rainbows, but a small fraction of these people are able to explain why rainbows are the way they are. Many of the physics principles we have learned this year can help explain why rainbows look the way they do.
The first principle is refraction. Refraction is something we have previously learned as bending light. This bending of light occurs because light can change speed. The speed of light in a certain media is always constant, but changes as the media changes. So as the light changes media it has to bend to accommodate for the different speed it is traveling. As the light changes from raindrops to air it undergoes refraction. Different colors refract at different angles.




The next component to understanding rainbows is the idea of white light. White light is something that we see everyday. However what we cannot see without proper tools is that white light can be broken down into all wavelengths of visible light. Basically when white light is separated, one can see that it is in actuality a mixture of all the different light types. The mixture would be a spectrum of all the different colors. A prism would be one such device that could break white light down into different spectrums. A raindrop can act as such a prism, dividing white light into different wavelengths. These wavelengths are ROYGBIV, or red, orange, yellow, green, blue, indigo and violet.



The next part of a rainbow to analyze is the way in which the colors fall. First of all the raindrops do not actually reflect mini rainbows that combine into one large rainbow. Each raindrop reflects a different single color because one raindrop would be far too small to reflect an entire rainbow. The raindrops that are located lower in the sky portray blue and greenish light, while the drops in the higher sky make up the red and yellow light. Because the single droplets do not make up the rainbow, there has to be something else to contribute to the entire rainbow picture. This is where the antisolar point comes in. It is the point that is 180 degrees away from the sun. This is essential to determining rainbows, more importantly where rainbows are in the sky. Along the antisolar line is also where the light that is being broken apart will be getting reflected. For one example red light gets reflected back at 42 degrees while blue light gets reflected back at only 40 degrees. This helps us understand rainbows because of how the colors are organized. The color red is placed on top for specific reasons. Each color of light has a different frequency, and when combined they form white light. But when separate each color is independent in terms of frequency and speeds. At different frequencies they refract in different ways as represented by the rainbow. Evidently these different concepts of everyday physics make something seen by all, able to be also understood by all.


Another miracle of everyday life are mirages. However they are not in fact miracles, because they after all can be explained by physics. Mirages rely primarily on refractions. Mirages can occur where different types of air congregate. As these different medias can congregate, refraction can be ongoing. And this refraction can produce the illusion of an image. This refraction occurs when the air near the bottom of the floor is a different temperature. So that this can be refracted at the boundary between the temperature difference, and then light from the sky will be reflected onto the floor. A mirage can also happen when there is a temperature difference in the air. Then in this case, with the right type of boundary, the image will be magnified in the distance. Mirages have fascinated people, because often times it is more interesting to believe in something else than a scientific explanation. Refractions of light in the sky can even account for some of the UFO spotting that occur around the world. Obviously these different types of mirages can occur and they can each be explained by something in physics.


Lastly the power of light refraction can help us explain some of the most widely acknowledged beauties of the world- sunsets and sunrises. People travel all around the world to find areas where the sunset or the sunrises are beautiful. However far fewer people are really interested in the physics behind these phenomena’s. They can be explained through the manner in which the eye works. The sun rays have to travel through several different parts of the universe and atmosphere before they reach our eyes. And as they travel through these parts they are refracted and broken down into the colors our eyes see. However the blue light is almost never seen due in part to the vast number of ways it refracts and how our lens works. If we use physics we can understand some of the most profound beauties of the world.



Bibliography

Metz, Dan. "How Rainbows Work." How Stuff Works. 2008. How Stuff Works. 2 Mar 2008 .

Gache , Gabriel. "How Mirages Work." How To. 14 12 2007. How To. 2 Mar 2008 .

Rayne, Edward. "Why does the red color appear at the horizon during sunset?." Physics and Astronomy Online. 2 Mar 2008 .

Sunglasses

Sunglasses
Kali Knickerbocker
Many people actually take sunglasses for granted. Believe it or not sunglasses are an essential when it comes to those summers spent on the lake and for those snow days in upstate New York. The sun can do an incredible amount of damage to your eyes and many people do not realize it. People do not realize that UV damage can build up over time. UV rays are an invisible form of radiation, and pelts our retinas at 186,000 miles per second causing various different problems (“Thermonuclear”). There are various ways in which manufacturers help to protect peoples eyes.
Sunglasses provide various different benefits from protecting your eyes from UV rays to being an added accessory. Good sunglasses protect your cornea and retina from ultraviolet light, which can cause various problems (“How”). Some of the most common problems caused by UV light include cataracts, photokeratitis and pterygium. Cataracts may begin as just making people nearsighted and eventually not able to see blue colors. Unfortunately it can also cause people to lose some vision and possibly even becoming blind (“Cataracts”). Photokeratitis can also be called snow blindness, it is a burning of the cornea. This usually happens at high altitudes and with snow (“Definition”). Pterygium is most common among people living in the tropical climates or those who spend a lot of time in the sun. This can also lead to blindness and is not pretty to look at (“Pterygium”). The sunglasses also protect our eyes from intense light. For example when an eye receives too much light it naturally closes the iris. When the iris closes as much as possible people then squint. Too much light coming into the retina causes damage to the retina. Sunglasses can also protect our eyes from glare. Surfaces such as water and snow reflect a great amount of light. As long as sunglasses are polarized they will protect from harmful glares(“How”).

~Cataract~
~Photokeratitis~

~Pterygium~

Polarized lenses main function is to reduce the glare and protect your retinas. Polarized lenses incorporate a vertical polarized filter, which then absorbs the horizontal light. This then eliminates the glare. A person is then left with a clear vision, increased contrast and depth perception (“Why”). One way to test and see if your sunglasses are polarized is to: look at a horizontal reflective surface, and then slowly tilt your head to the right or the left. You should notice that the glare off the surface brightens as you adjust the angle in which you are viewing the surface from. Buyers must be careful when purchasing sunglasses because many say they are polarized when in reality they may not be (“How”). There are various techniques that sunglass manufactures use to help sell products as well as protect buyers eyes.
((http://science.howstuffworks.com/sunglass2.htm) -Page 4 has a nice demonstration of this.)
Tinting is another part of sunglasses that help to protect eyes. The color of the tint determines which parts of the light spectrum are absorbed. For example, a gray tint reduces the overall amount of brightness. A gray tint also has the least amount of color distortion and have pretty good protection against glare. A yellow or gold tint reduces the amount of blue light, which allows a larger amount of other frequencies through. This tint can make everything brighter and sharper, and distorts color perception. The amber and brown tints are good for general use sunglasses. They definitely reduce the glare and absorb higher frequency colors, such as blue. The Green tints filter out some blue lights and also reduce glare. The green tine offers the best contrast and the best visual acuity; sunglasses with this tint are very popular. Purple and rose tints offer a very good contrast of objects against a green or blue background, which makes them good for hunting or water skiing (“How”). Various tints provide different benefits, be sure to explore your options before purchasing new sunglasses.
Another option dealing with sunglasses are the Photochromic Sunglasses. These sunglasses are often prescription glasses and darken when exposed to the sun. These lenses have millions of molecules of substance such as silver chloride or silver halide. Then the glasses are exposed to UV rays in the sunlight the molecules go through a chemical process which causes them to change shape. This new structure absorbs portions of the visible light, which causes the lenses to darken. These glasses to eventually switch back because when there is an absence of UV radiation the molecules snap back to the original shape. There are numerous different ways in which sunglasses can protect your eyes (“How”). Next time you go to purchase sunglasses take into account a couple things. It is understandable that you may want something to follow a trend in the fashion place but your eyes are more important. Every person is only given one set of eyes, which need to last his or her entire life. Your eyes need to stay protected from harmful situations. There are many manufactures today that combine the fashion and the needed amount of protection. Before purchasing a pair of expensive sunglasses make sure they provide the needed protection.

(Typical layering used to create a pair of high-grade sunglasses.)

Sources:

“How Sunglasses Work.” http://science.howstuffworks.com/sunglass.htm. February 25, 2008.

“Why are Polarized Lenses Important.” http://www.dentalplans.com. February 25, 2008.

“Thermonuclear Protection.” http://www.oakley.com. February 25, 2008.

“Pterygium.” http://www.stlukeseye.com/Conditions/Pterygium.asp. February 25, 2008.

“Definition of Photokeratitis.” http://www.medterms.com/script/main/art.asp?articlekey= 19394. February 25, 2008.
“Cataracts.” http://en.wikipedia.org/wiki/Cataract. February 25, 2008.

winter blog post

Phil Boyar
Mr. Wirth
Physics


Fiber Optics

The basis behind fiber optics links back to the physics of it all starting with the idea of total internal reflection. As light travels from an area such as air or water into another area or medium such as Lucite, diamond, back to air or water the light reflects and refracts. Each medium or area has a different or in some cases similar index of refraction. This index of refraction is represented by a number such as 1 for air, 1.33 for water, etc. When light crosses or reaches this barrier between mediums the light is both reflected and refracted at certain angles. In every case however, the light reflects at the same angle that it “came in,” to the cross between the mediums. You measure that angle from the normal. The angle of refraction however, can be measured by taking the sine of the angle of incidence and multiplying it by the index of refraction that the source came from and then dividing it by the index of refraction that it is entering. The final step would be to take the inverse sine of that decimal to find the angle of refraction. However, at the critical angle the refracted light will not go into the second medium and will travel along the surface between the media and the refracted beam will be reflected entirely back into the original medium. This is called total internal reflection. This phenomenon occurs when you take the sine of the angle of incidence multiply it by the index of refraction of the original medium and divide by the index of refraction of the second medium and the number you get is great or equal to one and the inverse sine of that number does not exist. This means that the light will not refract into the second medium but will only reflect back into the original medium. This phenomenon explains how fiber optics work from a physics and total internal reflection perspective.
Actual fiber optics are optical fibers that are long thing strands of pure glass, which can be put on a scale to equal approximately the size of a human hair. These individual strands can be bundled and arranged together into groups called optical cables which are used to send out light signals over longer distances. The actual optical fiber however, is composed of three main parts which combine to create its intricate design. The first part of the fiber is the cladding which is an outer material that surrounds the core and actually reflects the light back in to the core. The core, however, is the thin glass center in which the light travels. The last part is the buffer coating which is a plastic coating that protects the fiber from damage like moisture. Optical cables can contain hundreds or even thousands of these individual fibers and are safely protected from even more damage by the jacket. There are three different types of fibers. There are single-mode fibers, multi-mode fibers and optical fibers made from plastic. The single-mode fibers have a small core and send infrared laser light while the multi-mode fibers have large cores and send infrared light. However, the plastic made optical fibers have large cores and send visible red light like how LED screens work.
The actual cables function because the light in the cable travels through the core by continuously bouncing off the cladding, similar to how light bounces off mirrors, except in this case the cladding provides several mirrors so that the light can keep moving. The cladding is able to do this because it fails to absorb any light and can travel far distances which is a good thing. The light signal also can unfortunately degrade in the fiber because of either impure glass or the wavelength of the light.
There are now due to a great increase in technology, several uses for optical fibers. These uses range from telecommunication systems, medical uses, or anything that requires transmitting light to and from hard to reach places like a dentist’s drill. In addition in the medical field optical fibers are used to transmit images to view the inside of a body. In terms of the telecommunication application the fibers can be used underground or sea to transmit signals over long distances with a low amount of loss of signal. Another great thing about optical fibers are they are very cheap to build and use. They are used in telephones, internet, and pay television systems. Currently there are cables underwater that carry telephone and internet signals across the Atlantic and Pacific oceans. They are also used in those toys that light up at parties that appear to have lighted tips. Technology in this area can only grow to further possibilities because of how cheap and easy it is to use them, and because of its diverse abilities and functions. Fiber optics and the physics of total internal reflection are a great discovery that has benefited our society greatly and we would be unfortunate to not have the privilege of that technology. They are something that most people take for granted and do not think about and should be appreciated for how useful they are and how great they make the world today.

Works Cited

Craig Freudenrich, Ph.D.. "How Fiber Optics Work". March 06, 2001

http://electronics.howstuffworks.com/fiber-optic.htm (March 02, 2008)

Emily , McPherson . "Homework Help: Science: Physics: Fiber Optics." Jiskha:Homework help 1998 March 2,

2008 http://www.jiskha.com/science/physics/fiber_optics.html.

Human Eye

Larissa Loss
Winter Break Blog
Mr. Wirth
March 2, 2008


Anatomy:
The eye is a very complex organ in the human body. It is made out of various parts to function properly. In order for the eye to keep its round shape there is a tough, outer layer called the sclera. The front sixth of this layer is called the cornea. The cornea is where all light must first pass through before it enters the eye. The extraocular muscles control the movement of the eye. The muscular area that is attached the lens is called the ciliary body. It contracts and relaxes to control the size of the lens. The part of the eye which is colored is called the iris. The iris has two muscles, the dilator and the sphincter. The dilator makes the iris smaller, and therefore allowing the pupils to become larger and allowing more light into the eye. The sphincter makes the iris larger and the pupil smaller, therefore allowing less light into the eye.
The retina is the inmost part of the eye and controls the light-sensing portion of the eye. In the retina it has rod and cone cells. The rods are used for vision in dimmer light, while the cone cells control the color vision and detail. In the center of the macula which is located in the center of the retina, is the fovea centralis. The fovea centralis only has cones and is accountable for seeing detail very clearly. The rhodopsin which is located in the retina is responsible for changing light into electrical impulses that send messages to the brain to interpret the vision. The optic nerve which is located in the back of the eye consists of nerve fibers and which conducts the electrical impulses to the brain. The blind spot in the eye is called the optic disk, because there are no cone or rod cells located in that area of the brain.

There are six muscles attached to the sclera to control the movement of the eye. The six muscles consist of the medial rectus, lateral rectus, superior rectus, inferior rectus, superior oblique, and inferior oblique. The medial rectus controls the eyes moving towards the nose. The lateral rectus controls the eye moving away from the nose. The superior rectus raises the eye, the inferior rectus lowers the eye, and the superior and inferior oblique rotates the eye.

Vision: light and color:
The color vision in the eye consists of retinal and photopsins. There are three different kinds of color-sensitive pigments, red-sensitive pigment, green-sensitive pigment, and blue-sensitive pigment. The human eye can sense most colors when red green and blue are mixed together.
As light enters the eye, it eventually reaches the retina. In the retina contains rods and cones. Rods are responsible for vision in dim light, and cones are responsible for the color and detail. When light hits both cells a complex chemical reaction occurs. The chemical that is formed creates electrical impulses to the optic nerve. On the outer layers of the rods there is a chemical called rhodopsin. On the cones the chemicals are called color pigments. The retina contains millions of rods and cones and is pigmented black called melanin which lessens the amount of reflection and is responsible for sharp and detailed vision. The macula is the central part of the retina and has the highest concentration of only cones which provide the most clarity to our vision. Rhodopsin is a mixture of proteins and is unstable when exposed to light. This physical change causes rhodopsin to break down into several immediate compounds forming metarhodopsin II (activated rhodopsin). “This chemical causes electrical impulses that are transmitted to the brain and interpreted as light.”(Bianco). This is the primary visual cortex where visual interpretation occurs in the occipital lobe of the brain.

Normal Vision and Vision Problems:

Normal vision in the human eye is 20/20 vision. This is determined by reading a Snellen eye chart standing 20 feet away. However, not all people have perfect vision. Nearsightedness is when you can see things up close, but not far away. People who can see far away objects, but not close objects are farsighted. People with imperfect vision can be helped by wearing contacts or glasses.
The eye is an important and complex part of our body. We have natural defenses to protect it from harm. Our eyebrows prevent sweat from running into them and our eyelashes collect dust and dirt from floating in, as does our eyelid protect from foreign bodies. Tears are important for cleaning and constantly bathing our eye with moisture. We take our eyes for granted and forget how imperative they are for daily function.


Works Cited
Bianco Md., Dr. Carl. "How Vision Works." How Stuff Works. 1998. 2 Mar. 2008 .
"Your Sense of Sight." Sight. Think Quest Junior. 2 Mar. 2008 .

HUMAN EYE

How does our body convert one sort of energy like light to another? Sensory transduction explains this phenomenon. Sensory transduction is the conversion of one form of energy into another. In sensation, the transforming of stimulus energies, such as light, turns into neural impulses our brains can interpret. So how the eye works is that the eye receives the light energy and manage to transform the energy into neural messages that the brain then processes into what you consciously see.

Light Energy
Many people believe that its color that strikes our eyes, but scientifically speaking, it’s the pulses of the electromagnetic energy that our visual system perceives as color. The visible light on the spectrum is a thin slice of the rest of the spectrum of electromagnetic radiation. The human eye can see from the shorter waves of blue-violet light to the longer waves of red light. In interesting fact about vision is how other organisms are sensitive to differing portions of the spectrum. Bees for an example can’t see red but can see the ultraviolet light. Different organisms react to different stimuli. There are many physical characteristics of light that determine our experience of it. Light wavelengths is the distance from one wave peak to the next and this determines the hue such as the color blue, greed, red. Intensity is the amount of energy in light and it can be determined by the amplitude or height of the waves, but the importance of amplitude is that it influences the brightness of the color we perceive. Short wavelengths equals high frequency and humans see bluish colors. Long wavelengths equals low frequency and humans sees reddish colors. Great amplitude allows us to see bright colors while small amplitudes allow us to see dull colors.

The Eye
Although the eye is small in size, it is a very complex organ. You may ask How does the eye guide an incoming ray of light toward the eye’s receptor cells you might ask, how does the eye guide an incoming ray of light toward the eye’s receptor cells? Well, first the light enters the eye through the cornea which is a protective covering that bends the light ray. Then the iris, a ring of muscle, controls the size of the pupil, through which the light enters. The lens changes shape to focus light rays on the retina which is the inner surface of the eye where receptor cells convert the light energy into neural impulses. After the retina codes the neural impulses, the impulses travel along the optic nerve to the brain. The retina receives the image upside- down, and the brain constructs the impulses it receives into an upright- seeming image. After that explanation, other questions will arise like what are the different levels of processing that occurs as information travels from the eye’s retina to the brain’s cortex. Well, processing beings in the retina’s multiple neural layers and then the retinas 6 million cones and 120 million rods relay their information via bipolar cells to ganglion cells. The impulses travel along the ganglion cells’ axons which form the optic nerve to the thalamus and on to the visual cortex. In the visual cortex which features detectors respond to specific features of the visual stimulus. Higher level super cells integrate all the data for processing in other cortical areas. But in the cortex, our assumptions, interests, and expectations influences how we process sensory information. Then you may ask, what are the rods and cones you were talking about. Well, the rods and cones have different shapes, number, function, and location that link to the brain. When light enters the eye, it triggers a photochemical reaction in the rods and cones which in turn activates bipolar cells. The bipolar cells activate ganglion cells and there axons which combines to the form the optic nerve, transmits information via the thalamus to the visual cortex in the brains; occipital region. The 120 million rods located mainly around the periphery of the retina are more sensitive to light. Multiple rods send combined messages to a bipolar cell and the pool of information let us see rough images in dim light. It is used a lot of times for night vision. Cones are concentrated in the fovea which is at the center of the retina. They are sensitive to color and detail. A cone can link directly to a single bipolar cell, and this direct line to the brain preserves fine details in the cone’s messages. Also our eyes have blind spots. Blind spot is the point at which the optic nerve leaves the eye and it creates a “blind” spot because no receptor cells are located there. Now hopefully you have a better understanding of how the eye works and how it transforms one form of energy into another.

Normal Vision and vision problems

Errors of Refraction
Some people are nearsighted, and some people are farsighted and some people have normal vision. What does all this mean? Normal vision is when the rays of light converge on the retina of a normal eye. This occurs for both nearby objects and, with appropriate readjustments in the curvature of the lens, for objects far away. These people have 20/20 vision which means it means that when you stand 20 feet away from the chart you can see what a "normal" human being can see. A Nearsighted person is able to see near objects well and has difficulty seeing objects that are far away. Nearsightedness vision is when the light rays from distant objects focus in front of the retina. When their image reaches the retina, the rays are spreading out therefore blurring the image. A farsighted person is able to see distant objects well and has difficulty seeing objects that are near. Farsighted vision is when the light rays from nearby objects come into focuses behind the retina which results in blurred images.

Color Blindness
People who are color blind can’t differentiate between different colors. The most common type is red-green color blindness and it occurs in 8 percent of males and 0.4 percent of females. This happens when either the red or green cones are not present or not functioning properly. People with this problem are not completely unable to see red or green, but often confuse the two colors. Color blindness is an inherited disorder and affects men since the capacity for color vision is located on the X chromosomes. Males only inherit on X chromosome and females inherit 2 X chromosomes so they have a better change of not getting the disorder. Since the females have two X chromosomes, they have a higher change of inheriting at least on X with normal color vision. The inability to see any color, or seeing only in different shades of gray, is very rare.

Astigmatism
Astigmatism is an uneven curvature of the cornea and causes a distortion in vision. Today we can correct a person with astigmatism by correcting the shape of the lens and making it even. We use a lens that corrects the unevenness.

Works Cited

"How Vision Works." Howstuffworks "How Vision Works". 2008. How Stuff Works. 26 Feb 2008 >.

Myers, David G. Psycgolgy . VIII. New York: Worth Publishers, 2007.