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.

The Human Eye

Anatomy of the Eye, Vision: Light & Color, Normal Vision and Vision Problems.

Eyes are organs that detect light. The human eye is wrapped in three layers of tissue. The first layer is called the sclerotic coat. This tough layer creates the "white" of the eye except in the front where it forms the transparent cornea. The cornea admits light to the interior of the eye and bends the light rays to that they can be brought to a focus. The surface of the cornea is kept moist and dust-free by secretions from the tear glands. The next layer of the eye is called the choroids coat. This middle layer is deeply pigmented with melanin. It reduces reflection of stray light within the eye. The choroids coat forms the iris in the front of the eye. This, too, is pigmented and is responsible for eye "color". The size of its opening, the pupil, is variable and under the control of the autonomic nervous system. In dim light (or when danger threatens), the pupil opens wider letting more light into the eye. In bright light the pupil closes down. This not only reduces the amount of light entering the eye but also improves its image-forming ability. Finally, there is the most well known layer of the eye: the retina. The retina is the inner layer of the eye. It contains the light receptors, called rods and cones. The retina also has many interneurons that process the signals arising in the rods and cones before passing them back to the brain. All the nerve impulses generated in the retina travel back to the brain by way of the axons in the optic nerve. At the point on the retina where the approximately 1 million axons converge on the optic nerve, there are no rods or cones. This spot, called the blind spot, is thus insensitive to light.





In the human eye, light enters the pupil and is focused on the retina by the lens. Light-sensitive nerve cells called rods (for brightness) and cones (for color) react to the light. They interact with each other and send messages to the brain that indicate brightness, color, and contour. Although cones operate only in relatively bright light, they provide us with our sharpest images and enable us to see colors. Most of the 3 million cones in each retina are confined to a small region just opposite the lens called the fovea. So our sharpest and colorful images are limited to a small area of view. Because we can quickly direct our eyes to anything in view that interests us, we tend not to be aware of just how poor our peripheral vision is. Rods are extremely sensitive to light. A single photon (the minimum unit of light) absorbed by a small cluster of adjacent rods is sufficient to send a signal to the brain. So although rods provide us with a relatively grainy, colorless image, they permit us to detect light that is over a billion times dimmer than what we see when its sunny.




Most common vision problems occur in the lens. The lens is located just behind the iris. One common problem is Farsightedness. If the eyeball is too short or the lens too flat or inflexible, the light rays entering the eye — particularly those from nearby objects — will not be brought to a focus by the time they strike the retina. Eyeglasses with convex lenses can correct the problem. Farsightedness is called hypermetropia. Another common problem is called Nearsightedness. If the eyeball is too long or the lens too spherical, the image of distant objects is brought to a focus in front of the retina and is out of focus again before the light strikes the retina. Nearby objects can be seen more easily. Eyeglasses with concave lenses correct this problem by diverging the light rays before they enter the eye. Nearsightedness is called myopia. The term color blindness is something of a misnomer. Very few (~1 in 105) people cannot distinguish colors at all. Most "color-blind" people actually have abnormal color vision such as confusing the red and green of traffic lights. As high as 8% of the males in some populations have an inherited defect in their ability to discriminate reds and greens. Abnormal blue sensitivity occasionally occurs in humans but is much rarer than abnormalities in red-green vision. The gene for the blue-cone opsin is located on chromosome 7. Thus this trait shows an autosomal pattern of inheritance being found in females as often as in males.

Work Cited

Montgomery, Ted. “Anatomy, Physiology, Pathology of the Human Eye.” Ted Mongomery.com. 2000. 25 February 2008. <>.

“Eye Anatomy.” St. Lukes. St. Lukes Cataract and Laser Institution. 1998-2008. 26 February 2008. .

“Human Eye.” The Journey. The Journey Home. 2002. February 26 2008. .

Rainbows

Light is an important part of daily life. Growing plants use photosynthesis and light is a key component in this process. In order to hunt their prey or to escape a predator animals also need light. Some say that light has helped humans evolve into the complex beings that we are today. When we wake up in the morning until we fall asleep we are surrounded by light. Everything we look at in our surroundings is light. Do we ever stop and think about what we are actually seeing? Our eyes can only really see light, so are we really connected to these objects? On earth we can see one of the “most spectacular light shows.” This light show is a rainbow. How do we see the wide array of colors? It is all because of light (Freudenrich)!
A traditional rainbow is all different colors of the spectrum spread out and then diverted into the eye by small drops of water. Each raindrop contributes only one color to the rainbow that you see! Where is the sun when you see a rainbow? It was probably behind you while the rain was probably somewhere in front of you. Because the “sun is behind you and the rain is in front of you the sunlight must have been bouncing off the raindrops and reflecting into your eyes.” This is confusing because sunlight is primarily white light and that is what is reflecting off the raindrops, how do we see all of the colors of the rainbow? I found out that “these colors are present because the sunlight is not only reflecting off of the raindrops, but it is also refracting and dispersing in the raindrops.”
Rene Descartes was the first person to clearly discuss the formation of a rainbow by raindrops. In his studies he simplified the studies on rainbows by “reducing it to one rain droplet and how it interacts with the light falling upon it.”
He writes:"Considering that this bow appears not only in the sky, but also in the air near us, whenever there are drops of water illuminated by the sun, as we can see in certain fountains, I readily decided that it arose only from the way in which the rays of light act on these drops and pass from them to our eyes. Further, knowing that the drops are round, as has been formerly proved, and seeing that whether they are larger or smaller, the appearance of the bow is not changed in any way, I had the idea of making a very large one, so that I could examine it better.
Descartes describes how he held up a large sphere in the sunlight and looked at the sunlight reflected in it. He wrote "I found that if the sunlight came, for example, from the part of the sky which is marked AFZ

and my eye was at the point E, when I put the globe in position BCD, its part D appeared all red, and much more brilliant than the rest of it; and that whether I approached it or receded from it, or put it on my right or my left, or even turned it round about my head, provided that the line DE always made an angle of about forty-two degrees with the line EM, which we are to think of as drawn from the center of the sun to the eye, the part D appeared always similarly red; but that as soon as I made this angle DEM even a little larger, the red color disappeared; and if I made the angle a little smaller, the color did not disappear all at once, but divided itself first as if into two parts, less brilliant, and in which I could see yellow, blue, and other colors ... When I examined more particularly, in the globe BCD, what it was which made the part D appear red, I found that it was the rays of the sun which, coming from A to B, bend on entering the water at the point B, and to pass to C, where they are reflected to D, and bending there again as they pass out of the water, proceed to the point.”
This quote shows how the shape of the rainbow is explained. You can simplify this analysis by considering the path of monochromatic light through one raindrop. If you imagine how light is refracted through the raindrop, reflected inside the raindrop, curved, mirror-like surface of the raindrop, and last but not least how it was refracted as it emerges from the drop. We can apply the results for a single raindrop to a whole collection of raindrops in the sky. By applying these results we can visualize the shape of the bow.
What makes the colors in the rainbow? A traditional rainbow is made up of seven colors. ROY G. BIV (red, orange, yellow, green, blue, indigo, and violet). But despite that these seven colors are the ones visual to our eyes, a rainbow is actually a continuum of colors from red to violet and beyond these are colors that we can see. A rainbows color comes from two basic facts:
· “Sunlight is made up of the whole range of colors that they eye can detect. The range of sunlight colors, when combined, looks white to the eye. This property of sunlight was first demonstrated by Sir Isaac Newton in 1666.”
· Light of different colors is refracted by different amounts when is passes from one medium (air, for example) into another (water or glass, for example).
Two scientists, Descartes and Willebrord Snell, made a discovery. This discovery was how a ray of light is bent, this is also known as refraction, as the waves travel through different densities or materials. When light paths are traced through a raindrop, for example red and blue light, a person would find that the angles of deviation would differ. The blue light is refracted more than the red light.

The Picture below shows a faint secondary rainbow above then a bright primary rainbow. There are also several pastel-shaded rainbows inside the primary rainbow. While the additional rainbows can not be explained by geometric optics, they have their own term which is called “supernumerary.” But we do have explanations for the primary rainbow and the secondary rainbow. The primary rainbow comes from a “single internal reflection of refracted light inside a raindrop.” While the secondary rainbow results from “a double internal reflection (About Rainbows)”




In order to see a rainbow we need sunshine and falling rain. Rainbows are very rare. Rainbows are much rarer than we think. Halos are seen more frequently. The best times to see rainbows are in the late afternoon and the early morning because in order for us to see rainbows the sun cannot be too high in the sky. The lower the sun is in the sky the higher the bow is. A rainbow is not just a set of colored rings, the sky inside of the rainbow is bright as well because raindrops direct the light there as well (Bianco).










Works Cited

Bianco, Carl. "how stuff works." How Vision Works 02/21/2008 . http://www.howstuffworks.com/eye.htm.

Freudenrich, Craig. "How Light Works." How Stuff works 02/24/2008 .
The National Centor for Atmospheric Research & the UCAR Office of Programs. "About Rainbows." 2/29/2008 .

Rainbows, Mirages and the Color of the Sky and Sunset

There are many spectacular phenomenons in nature including rainbows, mirages, and the color of a beautiful sunrise or sunset. Often, these beautiful images seem unexplainable when actually they can be quite simply elucidated by the natural laws of physics. Rainbows, mirages, and the color of the sky and sunset are examples of how physics can make possible what seems impossible.
It is known that a prism is an object used to break down white light into different spectrums ("Rainbows"). The different spectrums that appear on the other side of the prism are the colors that make up a rainbow: red, orange, yellow, green, blue, indigo, and violet. The prism allows the colors to split up because each spectrum reacts to the class of the prism in a different way ("What Causes a Rainbow"). The glass forces each spectrum to bend, or refract, light at different angles which explains the separation of the colors ("Rainbows").
The idea of rainbows reinforces the concept of prisms. In a rainbow, each raindrop acts as a prism ("Rainbows"). Light enters a raindrop and is refracted through the other side and dispersed into different spectrums ("Rainbows"). Rays of sunlight that are refracted in a raindrop are the rays that create a rainbow ("What Causes a Rainbow"). Every raindrop that adds to the formation of a rainbow is responsible for only one color ("Rainbows"). For example, one raindrop might contribute to the blue ray of a rainbow, while another raindrop may add to the indigo ray. Although each raindrop does act as a prism and splits the sun’s light into all the colors in the spectrum, they are so small; only one beam of light is emitted that contributes to the overall rainbow ("Rainbows"). Raindrops that contribute red light are highest in the sky while those that contribute violet light are lowest. A point called the antisolar point, which is 180 degrees from the sun, determines where a rainbow is formed ("Rainbows"). Consequently, although a rainbow is a beautiful image, it can easily be explained by the laws of physics.
A mirage is another example of a phenomenon that physics helps us to understand ("Mirages"). Basically, mirages are created when there are two separate layers of air that are at different temperatures. The border between warm and cold air can bend light, similarly to a prism because cold air is denser than warm air ("Mirages"). This is essentially how a mirage is created. Often when the boundary between layers of warm and cold air is bent or curved, mirages act as mirror images of images far away ("Mirages"). They can also magnify these distant places and make them look much closer than they really are. A Fata Morgana is a mirage that occurs above water ("Mirages"). Before mirages were identified and explained, people saw them at sea and believed their destination was much closer than it really was. Mirages were even once thought of to be the work of witches ("Mirages").
There is also a physics explanation for the color of the sky at sunrise and sunset ("Blue Skies and White Clouds"). It is often wondered why the sky appears blue in the middle of the day, but red in the morning and evening. This can be explained by the laws of the scattering of light in the atmosphere ("Blue Skies and White Clouds"). During the middle of the day, or noon, the sun’s light passes through a thinner layer of atmosphere than it does during morning or evening. Not much of its light is scattered, which is the reason why it appears to be practically white ("Blue Skies and White Clouds"). Molecules in the atmosphere help to scatter the sun’s light. Humans see the sky as blue because the light being scattered is from the blue end of the spectrum.
This is not true of clouds, because water droplets that make up clouds are of a greater size than the molecules in the atmosphere that scatter the sun’s light. Because these droplets are larger than the molecules in the atmosphere, light is allowed to scatter color equally. Because color is being scattered equally, clouds are seen as white ("Blue Skies and White Clouds").
It is clear that even natural phenomenons such as rainbows, mirages, and the color of sunsets, sunrises, and the sky can be explained by physics’ simple laws. Because physics can help explain these natural occurrences, people are less fooled by mirages that create false images; astounded by the appearance of a rainbow, and puzzled over why the sky is red sometimes and blue at others. By looking at these examples, it is plain to see that physics can explain what was believed to be unexplainable.

Works Cited:

Department of Physics and Astronomy, Arizona State University. "Rainbows." Patterns in Nature: Light and Optics. 1995-2000. 20 Feb 2008. http://www.acept.id.asu.edu/PIN/rdg/rainbow/rainbow.shtml#top

Department of Physics and Astronomy, Arizona State University. "Blue Skies and White Clouds." Patterns in Nature: Light and Optics. 1995-2000. 20 Feb 2008.
http://www.acept.id.asu.edu/PIN/rdg/sky/sky.shtml.

Kryslek, Lee. "Mirages in the Sky." 1996, 1998. 20 Feb 2008. http://www.unmuseum.mus.pa.us/mirage.html.>

"What Causes a Rainbow?" How Stuff Works. 20 Feb 2008. http://www.howstuffworks.com/question41.htm.

Young, Andrew T. "An Introduction to Mirages." 1998-2008. 20 Feb 2008. http://www.mintaka.sdsu.edu/GF/Mirages/mirintro.html.