Sunday, March 2, 2008
Looking Into The Eye
This blog took a lot of work... but im glad it was for the blog versus just handing in a paper
-DLH
I spent way too long on this...(The human eye)
Although the human eye may seem small don’t mistake it for being a simple organ. The eye is only approximately one inch wide, one inch deep and 0.09 inches tall. The eye is made up of hundreds of key parts that work together to create your vision (howstuffworks.com). Without having eyes your life would be completely different.
Your eye is made up of three different layers, the sclera, the choroid, and the retina (all of them shown above). The sclera maintains the shape of eye and contains the cornea where all light passes through. The choroid is the second layer of the eye. This layer is extremely important because it provides blood to all the structures of the eye (howstuffworks.com). Without blood nothing will be able to function. The choroid contains two parts to it, the iris and the ciliary body. The iris is the adjustable colored diaphragm around the pupil which is the black opening on the eye. The ciliary body controls the size of the lens by contracting and relaxing it. The innermost layer of the eye is the retina. The retina contains two vital parts to it, rods and cones. The cones are responsible for color vision and detail while the rods are responsible for vision in low light. Another important part to the retina is the chemical it contains called rhodopsin. This chemical converts light into electrical impulses which the brain interprets as vision (howstuffworks.com). Below is a picture of a rod and a cone.
Seeing color also deals with the cones in our eyes. There are color-responsive chemicals in the cones that are called cone pigments and are very similar to the chemicals in the rods. There are three kinds of color sensitive pigments: red-sensitive pigment, green-sensitive pigment, and blue-sensitive pigment. Each one of the cones cells in each of our eyes has one of these pigments so that it is sensitive to that color. The human eye is amazing in that it can sense almost any gradation of color when, red, green, and blue are mixed (howstuffworks.com).
Normal vision is something doctors came up with after studying many people looking and trying to read off letters on a chart that is twenty feet away from them. 20/20 vision means that when you stand twenty feet away from the chart you can see what a “normal” human being can see. However, if you have 20/40 vision it means that you are no longer “normal” because you have to be twenty feet away from something to read or see it when a “normal” person can be forty feet away from it to see or read it. 20/200 vision is absolutely horrible vision and is the legal cutoff for blindness in the United States. People can also have better vision than the norm. If you have 20/10 vision then you can see something at twenty feet away when most “normal” people have to be ten feet away to see it (howstuffworks.com).
Some problems with the eyes include nearsightedness, farsightedness, and even blindness. Nearsightedness is when you can see objects up close well but far away objects are tough to see. This is caused by an eye ball that’s too long, or a lens system that has too much power to focus (howstuffworks.com). This problem can be corrected with the use of a concave lens as seen below:
Farsightedness is just the opposite. This occurs when a person is able to see distance objects especially well and has trouble seeing close up objects. This is caused by an eye ball that is too short, or by a lens system that has too little focusing power (howstuffworks.com). This problem can be corrected with the use of a convex lens as seen below:
There are many things that can lead to blindness. Cataracts, glaucoma, or just trauma to the eye are only a few of the things that can lead to blindness. A cataract is cloudiness in the lens that blocks light from reaching the retina. This condition usually happens as we age. As it worsens, it can require surgery to remove the lens and replace it with an intraocular lens. Glaucoma is caused when the aqueous humor of the eye does not drain out correctly. This causes pressure to build up on the eye. When this happens it causes cells and nerve fibers in the back of the eye to break and die. This can be treated with surgery or medications only. Another way to go blind would be by receiving trauma to the eye itself (howstuffworks.com). Getting hit, being poked, or having certain chemicals getting into the eyes can prevent adequate vision.
Brain, Marshall. “How Stuff Works”. March 02, 2008.
Your eye is made up of three different layers, the sclera, the choroid, and the retina (all of them shown above). The sclera maintains the shape of eye and contains the cornea where all light passes through. The choroid is the second layer of the eye. This layer is extremely important because it provides blood to all the structures of the eye (howstuffworks.com). Without blood nothing will be able to function. The choroid contains two parts to it, the iris and the ciliary body. The iris is the adjustable colored diaphragm around the pupil which is the black opening on the eye. The ciliary body controls the size of the lens by contracting and relaxing it. The innermost layer of the eye is the retina. The retina contains two vital parts to it, rods and cones. The cones are responsible for color vision and detail while the rods are responsible for vision in low light. Another important part to the retina is the chemical it contains called rhodopsin. This chemical converts light into electrical impulses which the brain interprets as vision (howstuffworks.com). Below is a picture of a rod and a cone.
Seeing color also deals with the cones in our eyes. There are color-responsive chemicals in the cones that are called cone pigments and are very similar to the chemicals in the rods. There are three kinds of color sensitive pigments: red-sensitive pigment, green-sensitive pigment, and blue-sensitive pigment. Each one of the cones cells in each of our eyes has one of these pigments so that it is sensitive to that color. The human eye is amazing in that it can sense almost any gradation of color when, red, green, and blue are mixed (howstuffworks.com).
Normal vision is something doctors came up with after studying many people looking and trying to read off letters on a chart that is twenty feet away from them. 20/20 vision means that when you stand twenty feet away from the chart you can see what a “normal” human being can see. However, if you have 20/40 vision it means that you are no longer “normal” because you have to be twenty feet away from something to read or see it when a “normal” person can be forty feet away from it to see or read it. 20/200 vision is absolutely horrible vision and is the legal cutoff for blindness in the United States. People can also have better vision than the norm. If you have 20/10 vision then you can see something at twenty feet away when most “normal” people have to be ten feet away to see it (howstuffworks.com).
Some problems with the eyes include nearsightedness, farsightedness, and even blindness. Nearsightedness is when you can see objects up close well but far away objects are tough to see. This is caused by an eye ball that’s too long, or a lens system that has too much power to focus (howstuffworks.com). This problem can be corrected with the use of a concave lens as seen below:
Farsightedness is just the opposite. This occurs when a person is able to see distance objects especially well and has trouble seeing close up objects. This is caused by an eye ball that is too short, or by a lens system that has too little focusing power (howstuffworks.com). This problem can be corrected with the use of a convex lens as seen below:
There are many things that can lead to blindness. Cataracts, glaucoma, or just trauma to the eye are only a few of the things that can lead to blindness. A cataract is cloudiness in the lens that blocks light from reaching the retina. This condition usually happens as we age. As it worsens, it can require surgery to remove the lens and replace it with an intraocular lens. Glaucoma is caused when the aqueous humor of the eye does not drain out correctly. This causes pressure to build up on the eye. When this happens it causes cells and nerve fibers in the back of the eye to break and die. This can be treated with surgery or medications only. Another way to go blind would be by receiving trauma to the eye itself (howstuffworks.com). Getting hit, being poked, or having certain chemicals getting into the eyes can prevent adequate vision.
Brain, Marshall. “How Stuff Works”. March 02, 2008
Physics of a Rainbow
Mr. Wirth,
My blog post essay is on my own blog. I wrote the blog on there last week and inserted pictures and now I'm not able to transfer the entire thing onto the class page altogether. So if you click my link you will see my post.
Thanks,
Courtney Sant
My blog post essay is on my own blog. I wrote the blog on there last week and inserted pictures and now I'm not able to transfer the entire thing onto the class page altogether. So if you click my link you will see my post.
Thanks,
Courtney Sant
Tuesday, February 26, 2008
The Crazy Fabulous Human Eye
By: Becky Salisbury
The human eye is a really cool part of the body. It is part of the nervous system and is what we see out of. It’s pretty weird to think that we see out of this tiny hole in our eyes, and the eye is a lot more fascinating than some people may think or care. First off, the human eye has three layers. The Sclerotic coat, the Choroid coat, and the Retina make up these three layers. This diagram shows those layers.
By: Becky Salisbury
The human eye is a really cool part of the body. It is part of the nervous system and is what we see out of. It’s pretty weird to think that we see out of this tiny hole in our eyes, and the eye is a lot more fascinating than some people may think or care. First off, the human eye has three layers. The Sclerotic coat, the Choroid coat, and the Retina make up these three layers. This diagram shows those layers.
So how does the eye work? Well, all the nerve impulses generated in the retina travel back to the brain by way of the axons in the optic nerve (also on diagram above.) The brain then does its thing, and that’s how we see! The lens (also above) is just behind the iris. This helps us to focus and adjust to see far away and close objects- just like a camera lens! The lens (eye’s lens that is) is held in place by zonules, extending from an encircling ring of muscle, called the ciliary muscle. Whether the muscle is relaxed or contracted decides whether the lens’ diameter increases or decreases, helping us adjust to see! Of course this system, like any system, is not perfect, and that’s where another type of lens comes in handy! (Glasses!). So what’s the deal about this? A too short eyeball, or too flat lens causes farsightedness, and too long eyeball or too spherical lens in contrast causes nearsightedness.
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/V/Vision.html
http://www1.istockphoto.com/file_thumbview_approve/2347508/2/istockphoto_2347508_close_up_of_eye_and_glasses.jpg
http://www.cancerhelp.org.uk/cancer_images/eye.gif
http://hyperphysics.phy-astr.gsu.edu/Hbase/ligcon.html#c1
Sunday, February 24, 2008
Thursday, February 14th, 2008
today the class period was spent going over the last quiz we took before break. the results of the quiz varied. there were many simple mistakes. the most confusion was in the last problem with a number of students not even knowing where to begin the problem to using 4 seconds as a time quantity rather than 2 seconds.
Friday, February 15, 2008
Tuesday, February 12, 2008
I like the idea about getting review packets for each topic that are styled after the Regents. I also like the visuals (slinky demo, video clips, etc) because I don't always understand what the notes are really saying but when I can see it I get it. The material we are covering now seems a lot easier than the stuff before the midterm; probably because I learned it years before.
Subscribe to:
Posts (Atom)