hey wirth im back

Scribe Post

Homework: Magnetism-Worksheet #1

Today in class we learned about The Right Hand rule, it tells the direction of the magnetic field around a conductor that is caring a current. The thumb pointing upwards tells the direction of the current, and the fingers which curl around tell the direction of the magnetic field. We also learned about solenoids which is wire wrapped around something often metal. Solenoids produce a magnetic field when an electrical current flows though them. Yes the Type-R does has solenoids.

Problem 63

Pieter van Musschenbroek invented the first capacitor, the leyden jar. It has a brass rod coming out of the top of an outer metal part. There is wood coating through which the brass goes through. The metal coating and wood keep the applied charge at equilibrium and do not allow it to be discharged. James Wimshurst invented the Wimshurst machine which creates strong electric charges. It has two insulated disks in the center of the machine which drive it, and as they rotate a strong charge is produced.

Problem No. 63, yo!

During the 17th and 18th centuries, several new inventions were developed to conduct tests and measure static electricity. The Leydan Jar for example, was a simple jar coated both inside and outside with foil. An electrode was then connected to a piece of foil inside the jar, which allowed electricity to be conducted. The charge then moves to the electrode with a generator. Another example of a fantastic machine was the Wimshurts machine. This machine was an electrostatic generator. In the generator there were rotating disks with metal attached to them. Though the only way it can be used is with the process of induction.

-Marcy

Chapter 24.1 #10-15

10. A magnetic field is definately present in nature because just use a magnet and you can see that they are vector quanities and exist.

11. Some magnetic forces around us are of course in magnets, by using a compass needle and magnet to see the affect it has on the compass to see the field. Also using bar magnets getting opposite poles facing each other will show the impact of magnetic fields.

12. If the currents are in the same direction, they will repel each other but if they are facing in opposite directions, the will attract because as the saying goes "opposites attract" and that is true in this case when dealing with magnets.

13. The magnetic field around a straight, current-carrying wire is numerous circular concentric circles around the wire.

14. The observable differences that will result are that the iron fillings will move opposite their original positions because they rely on the polarity of the poles of magnets and if those change, so do they.

15. a) The rod could behave this way because the poles are being moved and so the rods are probably just now attracting each other because of the switch because opposites poles attract and like ones repel.
b) The type of replacement rod that is used is a neutral rod.

63

Throughout the 17th and 18th centuries there were several new inventions developed to measure static electricity. One of these creations was the Leydan Jar. It made up of a jar coated inside and out with foil. Then an electrode was connected to the inside foil to conduct electricity. Then the charge moves to the electrode with a generator. Another invention was the Wimshurts machine. The machine is an electrostatic generator. The generator has rotating disks that carry metal on them. If the generator is used it is through the process of induction.

March 31

Equivalent resistance:
-the resistance seen by the source.
-equal to potential difference (V)/current (I)
Series Circuit:
-circuit with only one current path, with multiple drops in potential along the path
-example christmas tree lights
-current is the same in all components (I=I1=I2=I3=...)
-the sum of the potential drops is equal to the source potential (V=V1+V2+V3+...)
-the equivalent resistance is equal to the sum of the resitances and its components (Req=R1+R2+R3+...)
-ammeters must be connected in a series circuit so all current flows through it
Parallel Circuit:
-circuit with only one drop in potential with multiple paths for the current
-total current is the current supplied by the source. equal to the sum of the brance currents (I=I1+I2+I3+...)
-source potential is equal to the potential drop across each branch (V=V1=V2=V3=...)
-the reciprocal of Req is equal to the sum of the reciprocals of the resistance in each branch (1/Req=1/R1 + 1/R2 + 1/R3+...)
-voltmeters must be connected in a parallel circuit

Class Scribe Post-4/1

Class Lesson on 4/1-

Today we learned about the different meters in a circuit. Voltmeter, which is the measure of the potential difference between two distinct points on a circuit. It also has an extremely high internal resistance. We also learned about the ammeter, which is a measure of the current that passes through only one point of a circuit. In the ammeter, it has an extremely low internal resistance, differing from that of the voltmeter. The ammeter also creates an extremely small voltage drop while the voltmeter draws an extremely small current. At the beginning of the lesson we also discussed the difference between the potential difference in a parallel and series circuits through diagrams. We also did practice problems on white boards to better understand and grasp the concepts from previous lessons on circuits. The unit test was announced to be Monday on the material we learned today and the rest of the circuit stuff.

Chapter 20: #63

Throughout the 17th and 18th centuries, many breakthrough inventions were created in the field of electricity. One of these inventions was the Leyden Jar. It was constructed by taking a jar. The scientist would then coat the inside in foil and do the same for the outside of the jar. They would then connect an electrode to the inside foil in order to conduct electricity. The jar works by charging the electrode with a generator. The charge then moves into the foil. Another popular invention was the Wimshurst Machine. It was built by putting two discs spinning the opposite way. their would then be a spark gap between two metal spheres. The machine was poweered mechanically, not electrically. when the machine was cranked, it would make a spark between the two spheres.

3/25/08 Scribe

Today in class we went over electrical circuits. We started the class with a new list of scribes and did a warm up using circuit in a sentence. After that we started taking notes. One of the first ideas was the definition of a circuit which is a closed loop or path. Also charged particles move along said path, and which a electric current can exist and is formed by potential difference. In addition to that we went over some electrical schematics then we watched a four-minute video on electrical circuits. Some circuit elements that we went over included source elements, load elements, control elements and path elements. Finally we went over terms and definitions and learned the formula I = Δq/t and did some practice problems. At the end of the class we did a ticket to get out the door.
There was no homework!
justin d

we

#63

One thing used in the seventeenth and eighteenth century to study static electricity was the Leyden jar. This device consisted of 2 conductors separated by an insulator, usually tin foil on either side of a piece of plastic or glass. It is used by being charged by a static generator. The electricity flows into the jar and stays there. After being charged, a person can connect the conductors, causing a spark and the charges to discharge, resulting in the jar to be neutralized.
Another thing used to study static electricity is the Wimshurts machine. This decive is an electrostatic generator that has rotating disks with metal carriers in them. When used, the charges are produced by induction.

Problem 63

The Leyden jar is an early device for storing electric charge invented in 1745 by Pieter van Musschenbroek(1692–1761). It was the first capacitor. Leyden jars were used to conduct many early experiments in electricity.
The Wimshurst machine is an electrostatic device for generating high voltages developed between 1880 and 1883 by British inventor James Wimshurst (1832 – 19003). It has a distinctive appearance with two large contra-rotating discs mounted in a vertical plane, two cross bars with metallic brushes, and a spark gap formed by two metal spheres.

Chapter 20-#63

Chapter 20-#63

Several Devices were used in the seventeenth and eighteenth centuries to help scientists learn more about static electricity. One example is the Leyden Jar. This device was the first to be capable of storing large amounts of charge. First constructed in 1745, it was a glass vial filled partiallly with water and a thick conducting cable and the vial was sealed at the top with a cork. It was used to kill animals through electric shock in early households and was a breakthrough in the study of electrostatics. Another device used to study electrostatics was the wimshurst machine. Constructed of a generator, glass disks and metal carries, this device sent charges through induction. It is an excellent example of charge separation and a great early discovery that helped scientists learn more about static elctricity.

Blog Post for Fridays Class

• Went over homework


• Worked on a lab about static electricity

In this static electricity lab we detected the presence of an electric charge using a known charge. We used an electroscope to determine different charges of materials. We then built a table showing different charges of different objects, such as the black rod and the fur or the clear plastic rod and the silk.

• We were given graded homework from chapter 20 in the physics book.

question 63

The most important devises used to study electric energy in the 17th and 18th century were the Ledyen Jar and the Wimshurst machine. The Ledyen jar was discovered first in 1745, by Pieter van Musschenbroek. It was the first device that was able to store large amounts of electrical energy. With in a year of its creation, William Watson made some improvements on the constriction of the machine. It is a cylindrical container, made out of an insulator, with a layer of metal foil on either side of the cylinder. The outer side of the cylinder is grounded, while the inner side is given a charge. This enables the container to store electrical energy. The Wimshurst machine was created in the 1880s, by James Wimshurst. Unlike the Ledyen jar, the Wimshurst machine generates electrical energy, opposed to storing it. It is a machine consisting of two large contra-rotating discs that are mounted in a vertical plane, with two cross bars with metallic combs/brushes and a spark gap that is formed by two metallic spheres. The machine generates high voltages through induction. Within the machine there are quadrants of positively and negatively charged space, as the discs rotate, the metallic combs conducts the negative and positive charges away. Before this occurs, the machine already has an imbalance of charges, from human contact and such while it was being set up, and running the machine merely amplifies that imbalance.

Super physics fun time!

Here are some of the key important things that we learned yesterday during our fulfilling 8th period physics class:

-Charges in a system may be transfered from one object to another.

-Objects become electrically positive or negative when they have a deficiency or excess amount of e-.

-The formula Q=ne
q= total charge
n= number of elementary charge
e= elementary charge

Coulombs Law: The electrostatic force between two point charges is:
Directly proportional to product of charges, inversely proportional to square of distance between centers.

Formula: Fe= K(q1q2/r^2)
r= distance between centers of q1 and q2
k= electrostatic constant (k= 8.99 x 10^9 n-m^2/c^2

End of post.

Keil Kunzer
Mr. Wirth
Physics R
4 March 2008
The Human Eye

The human eye is a very complex structure of our body. Our eye gives a person the sense of sight and vision. The eye helps us decipher objects, colors, and shapes; it also can detect the difference between dim and bright light. There are many different parts to the human eye but the main ones are the iris, pupil, cornea, lens, and retina. Light waves enter the eye first through the cornea which is the clear part in the center of the eye. Then all the light gets processed in the pupil which is part of the iris. There are also many muscles in the eye that allow it to move and allow for our pupils to get bigger or smaller depending on the brightness of light rays. The human eye consists of many different complex parts, without these we would not have the ability of one of our most important senses (Montgomery).
Human vision is an extremely complex and interesting subject. The basic light sensing structure of the eye is the retina, which consists of both rods and cones. The rods and cones process the light through a chemical reaction, which then creates electrical impulses to the eye’s nerve. After the electrical impulses are sent to the nerve, this information is then sent to the brain where it is processed and then interpreted as light. In the cones are three different color sensing pigments. These colors include red, green, and blue color sensitive pigments. The eye can sense any combination of these colors unless a person has a color blindness disorder. Colorblindness occurs when one of the color pigments in the cones are not functioning properly. Colorblindness occurs in females in less than one percent of the population, but in males it occurs in eight percent of the population. The ability to see light and color is an extremely special feature of the human body, and it is something that many people take for granted.
Just because most everyone have the same eye structure, does not mean every human has the same vision. If someone is considered to have normal vision their vision is 20/20. That means the majority of the human population can see what you see at twenty feet. 20/10 vision is better than normal vision because it means you can see twenty feet of what a normal person can see when standing ten feet away from a vision chart. In the United States a person is legally blind when their vision is 20/200. A few vision problems a person might have are nearsightedness or farsightedness. When a person is nearsighted they have difficulty seeing objects that are close to them, which is caused by an elongated eyeball. The opposite is true for farsighted people, which is when people have trouble seeing objects farther away from them caused by a shorter eyeball. Another vision problem a person might develop is an astigmatism. An astigmatism is when the cornea is uneven or curved. This causes distortion to a person’s vision, yet this can be corrected with a lens that is fitted to correct the uneven cornea. The human vision system is an extremely complex structure of the human body (Bianco).
The human eye is an amazing organ, and gives people the great sense of vision. There are many people who are unable to see the everyday occurrences in their lives due to vision problems. It would be extremely difficult to live not being able to comprehend colors and frequencies of light.



Works Cited

Bianco, Carl. "How Vision Works." How Stuff Works. 4 March 2008
<http://health.howstuffworks.com/eye.htm>

Montgomery, Ted. "Anatomy, Physiology and Pathology of the Human
Eye." 4 March 2008 <http://health.howstuffworks.com/eye.htm>

The Human Eye

Luke Seavitt

Physics blog post

Wirth

The Eye:

Although the human eye is one of the smallest human organs it is one of the most complex. It is composed of several different parts that all work together to help us see the objects that we look at. In order for the eye to maintain its shape it has something called the sclera which is the outermost layer of the eye. The front sixth of the sclera is called the cornea and this part of the eye is also clear. All light that is seen by the human eye has to pass through the cornea. Also attached to the sclera are muscles that provide movement to the eye. These muscles are called extrocular muscles. Blood vessels that supply blood to the eye are located in the second layer of the eye which is called the choroid. The front part of the choroid is composed of two parts the ciliary body and the iris. The ciliary body contracts and relaxes to control the size of the lens for focusing. The iris is the colored part of your eye and is determined by the color of the tissue and pigment cells. The iris itself has two muscles. It has the dilator muscle which makes the pupil larger allowing more light through the eye and making the iris smaller. The sphincter does the opposite of the dilator and makes the pupil smaller by increasing the size of the iris allowing for less light to go through the eye. The intermost layer of the eye is the retina which is the light sensing part of the eye. It contains cells called rod cells that are in charge of vision in low light. It also has cone cells which are responsible for color vision and detail. Another part of the retina is located in the back called the macula. In the center of the retina is something called the fovea centrails which is responsible for seeing small details. Also in the retina is something called the rhodopsin that converts light into electrical impulses to send to the brain to interpret the visions. The retina also has nerve fibers at the back of the eye which form the optic nerve, which conducts the electrical impulses to the brain. The spot where the optic nerve and blood vessels exit the retina is called the optic disk. This area is a blind spot on the retina because there are no rods or cones at that location. However, you are not aware of this blind spot because each eye covers for the blind spot of the other eye. In order for the scela to move the eye it has six different muscles to move the eye. The medial rectus which moves the eye towards the nose and the lateral rectus which does the opposite of the medial rectus and moves the eye away from the nose. It also has the superior rectus which raises the eye and the inferior rectus which lowers the eye. Lastly it has the superior oblique and inferior oblique which both rotate the eye.

Light and Color:

The eye perceives light first through the cornea then the aqueous humor, lens and vitreous humor. Eventually the light reaches the retina which is the light sensing structure. It contains two cells which are rods and cones. The rods handle the vision in low light and the cones handle color vision and detail. When light contacts these two types of cells, a series of complex chemical reactions occurs. This creates electrical impulses that in the optic nerve. In order to see color the eye has color responsive chemicals in the cones called cone pigments and they are very similar to those found in the rods. The retinal portion of the chemical is the same, however the scotopsin is replaced with photopsins. There are three kinds of color-sensitive pigments, red, green, and blue sensitive pigments. Each cone has one of these pigments so it is sensitive to that color. The peak absorbancy of blue-sensitive pigment is 445 nanometers, for green-sensitive pigment it is 535 nanometers, and for red-sensitive pigment it is 570 nanometers.

Refraction:

The eye has multiple angulated surfaces that cause light to bend. These are the interface between the air and the front of the cornea, the interface between the back of the cornea and the aqueous humor. Also the interface between the aqueous humor and the front of the lens and the interface between the back of the lens and the vitreous humor. When every one of these are working perfectly, light makes it through these four interfaces and arrives at the retina in perfect focus.

Normal Vision and Vision Problems:

The normal vision of a human being is 20/20 vision. This is determined by looking at the Snellen eye chart at a distance of 20 feet. If you have 20/20 vision, it means that when you stand 20 feet away from the chart you can see what a "normal" human being can see. However, not all people have perfect 20/20 vision. People can be nearsighted or farsighted meaning that they can either only see up close or they can only see from far away. To fix their vision many people wear eye glasses or contacts. There is also another problem that can occur with the eye called Astigmatism, which is an uneven curvature of the cornea and causes a distortion in vision. To correct this, a lens is shaped to correct the unevenness.

Bianco Md., Dr. Carl. "How Vision Works." How Stuff Works. 1998. 4 Mar. 2008 .

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

Fiber Optics - John Tedesco

John Tedesco

Mr. Wirth

Physics R

3 March 2008

Physics Blog Post: Fiber Optics

Fiber Optic Cables are one of the most widely used forms of sending information in the twenty first century. Fiber Optic cables are one of the fastest ways of communication, whether it is through the internet, television, or other devices such as telephone (How). In addition, they are very reliable and efficient, drawing more and more companies to use them each year. Millions of Americans use fiber optics in their internet cables instead of DSL. In addition, fiber optic powered internet is light years faster than road runner, something we think is fast. Many major Metropolitan cities such as Pittsburgh are using fiber optic cables for the majority of their internet use.

Many people are not familiar with this new and efficient technology. Fiber optics is a thin piece of glass about the same size of a single human hair. These thin strands of glass are packaged together in cables and are used to transfer information. Fiber optics consists of three main parts. The core is in the center and is pure, thin glass used to carry the light through the cable. Around the core is the cladding, which provides as a barrier in order to keep the light inside of the core (How). This is able to occur due to total internal reflection, which is when light is unable to escape from the core because of the properties of the cladding. If light tries to escape the core and move onto the cladding, it is unable to due to the difference in the indices of refraction between the core and the cladding (Homework). Surrounding the cladding is the buffer coating, whose only function is to minimize damage to the fiber optics. Thousands of fiber optic cables are then bundled up and are surrounded by jackets, making them the cables that we know today.

[img]http://static.howstuffworks.com/gif/fiber-optic-fiber.jpg[/img]

There is a vast amount of physics behind the uses of fiber optics. All of it surrounds the principle of total internal refection. Total internal reflection is when light cannot pass from one medium to another because of the differences in the indices of refraction. In fiber optics, light is trapped in the core, because the angle of incidence at the surface of the cladding is greater than the critical angle (Homework). This means that the light remains trapped inside of the core and continues to travel at 300,000,000m/s through the cable. This results in the most efficient and by far the most affordable form of communication in the world today.

[img]http://hsc.csu.edu.au/senior_science/core/info_systems/9_4_6/Laserpath.gif[/img]

Fiber optics holds many advantages when compared to other forms of communication present in modern times. It is more efficient, less expensive, it takes up less space, it is faster, it is non-flammable since it uses light instead of electricity, it uses less power, and it can be used in medical imaging (How).

Fiber optics is by far one of the most promising technologies of the day. Taking advantage of light, fiber optics is one of the fastest forms of communication in the world, and it holds promising results for the future.

Citation

"Homework Help: Science: Physics: Fiber Optics." Jiskha Homework Help. 2 Mar 2008 .

"How Fiber Optics Work." How Stuff Works. 2 Mar 2008 .

http://hsc.csu.edu.au/senior_science/core/info_systems/9_4_6/Laserpath.gif

The Human Eye

Mary Posman

The Human Eye
The eye is an intricate and sophisticated structure that enables humans to perceive the world; without which our world, literally, would be dark.
The eye has many complex sections that work together to create the images that we see everyday. Generally the eye is approximately one inch wide, one inch deep and 0.9 inches tall. The sclera is the outermost layer of the eye and its function is to maintain the shape of the eye. Six muscles are attached to the sclera that work together to control the movements of the eye: the medial rectus, which moves the eye towards the nose, the lateral rectus which moves the eye away from the nose, the superior rectus, which raises the eye, the inferior rectus, which lowers the eye, and the superior and inferior oblique, both of which rotate the eye (Bianco). Covering the sclera is a mucus membrane, called conjunctive, which keeps the eye moist.













The cornea is the clear, frontal section of the sclera, which allows light to pass into the eye. The second layer of the eye is the choroid, and supplies blood to the eye. The choroid is composed of two sections, the ciliary body and the iris. The ciliary body is a muscular section attached to the lens, it controls the focusing of the lens by contracting and relaxing. It also produces a liquid solution called aqueous humor, which is located in the front of the eye. The aqueous humor is one of two liquid solutions found in the eye, the other is vitreous humor, which is a gel like substance located in the back section of the eye. The iris is the colored part of the eye and contains two muscles, the dilator and the sphincter. When the dilator contracts, it makes the iris smaller, while the sphincter relaxes to make the iris larger. This controls the amount of light that is let into the eye through the pupil. The picture to the left is an example of the dilator at work, the iris is large, making the pupil small. While on the right is an example of the sphincter, the iris is small, making the pupil larger (Your).
The innermost layer of the eye is the retina, the retina is the light sensing area of the eye. Within the retina there are cells called cones and rods, which detect color and shapes respectively. There are approximately one hundred and fifty million cones and rods in the retina (Your). Both of these are important to our visual processing and will be discussed in more detail later on. The macula is also found in the retina, it is in the center of the retina, the macula contains the fovea centralis, which only houses cones. There is also the chemical rhodopsin, or “visual purple” within the retina, which converts light into electrical impulses that are sent to the brain for interpretation (Bianco). The electrical impulses are carried to the brain by the optic nerve, this is the collection of retinal nerve fibers that collect at the back of the eye. Passing through the optic disk , which is where the optic nerve and blood vessels exit the retina on their way to the brain.. When all of these sections are put together, the eye is formed and fully operational.
















Like the eye itself, the process by which humans are able to perceive light and color is also complex. When we perceive light, it must first pass through the cornea, then the aqueous humor, lens and vitreous humor before reaching the retina (Bianco). The light is refracted slightly by the aqueous humor, then a little bit more by the lens and vitreous humor. The lens is responsible for forming the shape of the image, it is able to adjust quickly to different objects by the process of accommodation. The ciliary muscle relaxes and contracts, changing the shape of the lens to adjust to the objects size and distance (Polarization). Once the light reaches the retina it comes in contact with rods and cones, this contact causes chemical reactions to begin in the eye. Activated rhodopsin is created, as mentioned before this generates electrical impulses to the optic nerve. When light enters the rods, it contacts rhodopsin and causes it to decompose into all-trans retinal, which is unstable and decomposes further to metarhodospin II. This is the chemical that actually creates the electrical impulses that are transmitted to the brain (Bianco). When these messages are perceived in the brain, they appear upside down, it is then the brain’s job to flip the images right-side up, this process occurs in the visual cortex (Your).











While the process of perceiving light mainly occurs in the rods, the perception of color takes place largely in the cones. The actual process of perceiving color is similar to that of light, the main difference is that the chemical photopsin replaces scotopsin (see chart above). Also, there are three color-sensitive pigments within the cones, these pigments sense red, green and blue. Each cone has one of these pigments and by various blends of these pigments, we are able to perceive almost any color (Bianco). Both of these processes occur at the same time, allowing humans to perceive the light, shapes and colors of the world.
When all is functioning properly, humans are able to “see” the world around them clearly and in focus. Visual acuity is tested by the Snellen eye chart, which is a chart of letters in rows, decreasing in size from the top row.







http://www.contrastsensitivity.net/images/echart.jpg
Normal vision is defined as 20/20, which means that at twenty feet away from the chart you can see the same amount of accurate letters as most people see from twenty feet. 20/40 means that you have less than normal visual acuity and can only see what most people can see at forty feet away. It is possible to have better than normal vision, 20/10 for example. This means that at twenty feet you can see what most people can only see at ten feet away (Bianco). Depth perception is another part of normal vision, this enables humans to decipher how far away an object is. There are three main processes by which humans determine an object’s depth/distance. The first is the amount of space the object takes on the retina. If the object takes a large place on the retina, the brain will determine that it is closer, while an object that is farther away would take up less space on the retina. Secondly, when we move our head side to side, objects that are close to us move rapidly across our retina, and appear as a blear moving past us, while those that are farther away move across our retina at a slower pace and appear more clearly (Bianco). Here’s an example, imagine that you are looking out the car window, the trees that are right at the edge of the road appear in a blur of green and brown, while we can clearly see those that are farther away. Thirdly there is stereo vision, each eye receives a different image since they are about an inch apart. The brain interprets the differences in these images to determine the location of the object (Bianco).
Since the process of vision is complex, there can be many errors and problems that occur. One of which is color blindness, this is the inability to differentiate between colors. This affliction is more common in men, since it is an inherited effect and the capacity of color vision is in the X-chromosomes and women have two. The most common type of color blindness is the inability to differentiate between red and green. In this case either the red or green cones are not present or they do not function properly (Bianco).












http://www.colormatters.com/kids/images/cones_color.jpg
Another failure in vision is night blindness, which is caused by vitamin A deficiency. Vitamin A is necessary to form retinal, a part of the rhodopsin molecule that that senses light. A lack of these light sensing molecules causes an inability to see at night, since there is not enough light (Bianco). This is less common, but its does still occur. Astigmatism is more common, especially as people age, and is a curvature of the cornea that distorts vision. This can be corrected by creating a contact lens that corrects the curvature of the cornea. Troubles with refraction also cause visual problems such as nearsightedness and farsightedness. Nearsightedness, or myopia, is when a person can see things clearly up close, but not far away. This is caused by an eyeball that is, in essence, too long.







(Your)
The light rays don not quite reach the retina, and are focused instead, on the front of the retina. This can be corrected with concave-lenses, which will cause the light to diverge slightly before reaching the eye (Bianco).












Farsightedness, or hyperopia, is when a person can see things at a distance, but not close up. This, is the opposite of nearsightedness and is caused by an eyeball that is too short.








(Your)

The shortness of the eyeball causes the light rays to go pass the retina. This can be corrected with convex lenses (Bianco).










While these are minor problems that can be corrected for the most part, there are also many causes of blindness.
Blindness is technically defined as vision that is less than 20/200 and can have many different causes. One such cause is cataracts, which are cloudy substances that form on the lens, preventing light from reaching the retina. These are more common with age and can be corrected with surgery.






http://www.ehponline.org/docs/2005/113-3/eye.jpg
Glaucoma is another cause a blindness, this occurs when the aqueous humor does not drain correctly, causing pressure to build up in the eye killing cells and nerve fibers in the back of the eye. This can also be corrected with surgery or medicine (Bianco). Diabetic retinopathy also causes blindness in people with diabetes. It occurs when there is a blockage, leakage and/or scaring of blood vessels in the eye. However, it can be cured with laser surgery. There is also macular degeneration, the macular is responsible for fine-detailed vision, it begins to deteriorate, and eventually all central vision is lost. Sometimes this can he helped with laser surgery, but not always (Bianco). Trachoma is an infection that is caused by Chlamydia trachomais and eventually leads to blindness, however it can be cured with antibiotics. Another form of blindness is caused by retinitis pigmentosa, an inherited disease that causes blindness by degenerating the retina and excess pigment that allows humans to perceive light. It is a degenerate process, beginning with night blindness, then tunnel vision then complete blindness. There is, unfortunately, no known treatment for this disease. Trauma can also cause blindness, especially if it involves chemical injuries that damage the eye (Bianco). While these are some of the most prevalent causes of blindness, there are many others including strokes and neurological diseases. While these cases of blindness exists, most people are fortunate and have accurate vision, or vision that can be corrected with glasses or contact lenses.
The eye is a fascinating mechanism that is critical to man’s survival. Man’s existence is centered on the proper functioning of the eye, and today we are lucky to have the technology to correct many dysfunctions of the eye. The eye’s processes of vision, and the physics that accompanies it is an intriguing and necessary part of life.



Bibliography
Bianco, Carl. "How Vision Works." How Stuff Works. 26 Feb 2008 http://health.howstuffworks.com/eye.htm.

"Polarization; and The Huamn Eye." PY106-Elementary Physics II. Boston University. 29
Feb2008 http://physics.bu.edu/~duffy/PY106/Eye.html.

"Your Sense of Sight." Think Quest Junior. 29 Feb 2008 .

weekly blog

This week we mostly did review, which I thought was helpful. This unit has been kind of long, so I think this week of review was a good idea before the test on monday. I really like that you give out review packets and the answers so we can learn what we need to study and what we already know. Hopefully all of this will pay off and the test will go well on Monday.

Wednesday February 13

Refraction- the change in direction upon transmission into a new medium if the wave a) changes speed b) strikes a boundary obliquely (not perpendicular)
Examples of different media of refraction: glass, air, water

Rules:
-If speed decreases at interface, then the wave bends toward the normal
-If speed increases at interface, the wave bends away from normal

Absolute index of refraction- the ratio of the speed of light in a vacuum to the speed of light in the medium. (dimensionless) Symbol= n

Equations:

n2=v1=λ1
n1 v2 λ2

n=c/v

Example:
What is the speed of light in water?

c= 3.0x10⁸ m/s
n=1.33

n=c/v

1.33=3.0x10⁸ m/s / v

v=2.25x10⁸ m/s

February 15, 2008

In class today we watched a movie about the different job fields that are associated with physcics and chemistry. We saw that there were numerious amounts of different applications of the skills that are learned in physics and chemistry. There are several engineering applications in the world today that involve both physics and chemistry such as mechanical engineering, biomedical engineering, and electrical engineering. Overall the day was more about seeing what type of jobs are out there if we continue to study science in college and want to have a career related to physics and/or chemistry

Thursday Class Post

On Thursday we spent the majority of the class reviewing the quiz on waves. This quiz was more like the midterm back in January then like previous quizzes. I liked the variety of question methods of multiple choice, graphing and short answer. I thought that some of the questions were similar to what I would have expected for this quiz. I thought that the information was for the most part from the notes and i just made a few careless mistakes. In this unit if you confuse one thing, it can really throw you off. I also got tricked by the last question because i did all the math right, i just did not realize it was roundtrip so i messed that up. Overall i did not think that the quiz was too bad, i just confused a few things and it threw me off, but the quiz corrections have helped clear up the confusion and i now i understand this unit better.

weekly post

We gotthe quizes back, and it went how I thought it did, I just made a bunch of really stupid mistakes, or like reversed concepts in my head. Going over it helped, and explined things that I didn't get. Thanks for taking the time to do that, and allowing us to do the corrections in class.

Also, letting us use some lab time to learn how to use excell was helpful. But I don't know if you really need to devote an entire lab period to that tutorial thing, since there weren't examples/opertunities to do things ourselves. It might be helpful in the future to leave that link on the site, and just make the labs be done with excell and be a bit leniant in the begining with grading on the format. This way if we did get stuck, we could just check the tutorial.

comment

i agree that we learned about waves and frequency....i believe that the pre-quiz is a good guide to what the quiz is gona b on

weekly blog

So, I just finished the quiz, I did't think it was that bad, but there were some things that I didn't know. A couple of questions seemed new, like we hadn't done things like that in class. That seems to happen often with these quizes, that some of the questions are new and random. Its kind a of aggrevating if you do the practice stuff, and then stuff that isn't on those review sheets are on the quiz.

Waves Part II

Yesterday in class we continued learning about waves. We learned about standing waves, which travel in the same medium, have the same frequency and amplitude, but travel in oppisite directions. We watched a video clip and saw some demonstrations to further explain this concept. I think that maybe just one or the other, the deomstration or the video would have been enough, both was kind of over kill and just seemed repetitive.

Then we learned about diffratcion, which is what happens after a wave hits an obsticle, like a wall with a break in it. After it hits the wall, the wave spreads out behind it. Once again, the picture were helpful here, but the video seemd a bit redundent. I think its good to break up notes every once in a while, but too many videos makes the lesson kind of chopping.

Finally we learned about resonance, which is the amplitdue of an object's ocialtion at or near its normal frequency. Once again we were given exaplmes to better understand the concept.

Waves Doppler Effect

In class we leared about Waves and The Doppler Effect. The Doppler Effect is a varation in the frequency when there is relative motion between the source of the frequency and the observer. If the source is approching there will be a higher frequency and if it is Receeding there is a lower frequency. An example of The Doppler Effect is the fire truck siren, which was talked about in class.

MIDTERM

The midterm was down right awful!!!! We spent time reviewing for those past few days before it, but that still wasn't enough!! Some questions were easy, but most were not. This made me a sad panda. Oh well, I can only hope I do well on the final. Lets get working on the new material!

Midterm Reflection

Midterm Reflection

I thought that the midterm was not too bad except for the trajectory and other stuff that we did not review as much. Some of the questions I felt were more focused on the smaller units we covered rather than the ones we spent more time on. I think that some of the multiple choice questions were tricky and others we really straight forward. Overall I think the midterm was ok but certain parts were alot harder than others.

Mid term

I didn't think the mid term was too difficult, but I thought I had done better than my grade reflected, still I think I did pretty well. The review packets that Mr. Wirth gave us were really helpful, since some of the problems on the mid term were similar. Something that would have made those packets even better would be if the answer key showed how to get an answer instead of just idnetifing that it was A,B,C or D. That way we could learn from our mistakes.

Midterm Exam

I thought that the midterm exam was a little bit harder than i expected. However, it was still a pretty descent test. One way i could have increased my grade was to study the packets that we were given. Mr. Wirth really couldn't have done anything differently. Overall i think i did pretty good on the midterm.

Mid-term reflection

i thought that the midterm was more difficult than i expected. i don't think that i did enough problem preparation for the test. I reviewed the summary packets and memorized concepts but they wern't terribly useful without knowing how to use them on actual problems. I also thought that some of the problems on the midterm were somewhat new material (i.e. we had not gone over in class). I could have made more of an effort to come in and practice problems instead of just reviewing the packets.

Mid-term

i found the midterm to be harder than i expected because the questions seemed more difficult than the ones i was used to doing in class. i think i could have prevented that by doing the practice problems in the review packets instead of just going over my notes and the summaries in the packets and by studying more in advance so if i had any questions i could have came in and asked questions on the topics i had more trouble in

Mid-term reflection

Before i went into the exam i felt pretty confident since i had gone through all the packets Mr. Wirth gave us and did pretty well on them, so I felt prepared. After I took the midterm I thought i didn't really well because it didn't seem to hard however my grade was a little different than I expected. To have improve I could of put more work into studying for physics and paying better attention in class. The only thing I think Mr. Wirth could have done better is give all of our tests as regents type questions to better prepare us for the format of the test.

I thought I was prepared and had a full grasp of the material. However I thought I did better than my actual grade indicated. One suggestion for improving my grade would be to have a small study group before the test. I don't think Mr. Wirth could have done anything different and I think because I've missed a month of school my grade was lower than it otherwise could have been. I think it would be beneficial to have updated physics videos or remove them completely on the other hand if the physics classes don't want to learn it won't matter what videos are used

1/10/08-Work and Energy

Today in class we learned about work and energy. Work is a force acting through a distance. It is also an energy relationship. The formula for work is Work= Force x Distance, or W=FD. Work is also equal to the change in total energy.
We were also introduced to a new formula for total energy: Et=KE+PE+Q. Therefore, Work equals change in PE+ change in KE+ change in Q.
Q is the symbol for internal energy. This is the total kinetic energy and the total potential energy of all the individual molecules and atoms. This includes chemical potential energy and nuclear potential energy.
I think that we need to spend less time in class on definitions and more time on problem examples, particularly the more challenging ones. I feel that we spend too much time going over similar easy problems and not concentrating on moderate to more difficult examples that appear on our quizzes.

1/07/08



Today we learned about Kinetic Energy. Kinetic energy is the energy of a body or a system with respect to the motion of the body or of the particles in the system. Also we learned how most of us failed the quiz that we took, except for me. I think everyone needs to spend more time thinking about physics. We need to think about physics all the time, therefore this blogger site may help students get more fluent with the physics language. Also during class there have been too many interuptions, I wont name peoples names but you should know who you are. It is hard to teach a 40 minute class with people having side conversations all the time. I have been hearing complaints about how people don't understand certain material, and maybe if our class concentrated more during the class we wouldn't have these problems.

Model Post for 1/4/07 - Energy and Power

We started today's class with a review of last night's homework, which was a problem set on "power". The most difficult problems were on the back page, where we had to recognize that we could change the power equation P=W/t into P=Fd/t and then into P=Fv, where v is the velocity of the object. So if you know the force being applied, and the velocity, you can calculate power. You don't need the actual distance traveled.

We then went over two topics - one connected to yesterday's video that mentioned the dot product between two vectors, and the other related to graphing. The dot product that we saw yesterday provides a way to calculate the component of the force in the direction of motion when we calculate work, and today we saw the equation we should use - W = F x cos(theta) x d, where F is force, d is the distance over which the force acts, and theta is the angle between the applied force and the direction of motion. Here's the equation clipped from the online notes:












We worked through an example of this and then we discussed the idea of graphing force versus distance and how the area under that curve becomes the work done, shown below:
Next we began learning about energy and the different forms it can take, and most importantly, the definition - the ability or capacity to do work. It has the same units as work (the joule), and is directly related to it. Energy is conserved, meaning it does not get created or destroyed, and only gets exchanged between objects, systems, or forms. The total is always the same. Kinetic energy (the energy of motion) and potential energy (stored energy) are the two types that make up mechanical energy, and their sum (KE + PE) equal the total mechanical energy of an object or system.

We did a few examples of calculating KE, and then finished up with a review of the weekend blog assignment, which is to read the existing posts on our "Home Base" blog, and the model post you are now reading, and leave a "thoughtful" comment on one of them. Monday we will start writing scribe posts for real.

Scribe List - Period 8

This is the SCRIBE LIST. To simplify the process, we will go in the order listed (which is alphabetical). You may swap with someone if you'd like.

Scribes - Cycle Starting 3/25

Manny-3/26

Justin-3/25

Dan -3/27

Keil-3/28

Grace3/31

Elizabeth- 4/1

Mary-4/2

Marcelo-4/3

Keaton

Luke

John

Chloe

Marlies