Tuesday, August 16, 2011
Friday, August 5, 2011
Please get the following completed.
Name / ID (Register Number) /Class
Remember to submit your homework.
Thursday, August 4, 2011
Fiber-optic communication (The process):
1. Can be used over greater distances due to the low loss, high bandwidth properties
2. It can be used for 2km without the use of a repeater
3. Their light weight and small in size, which makes them ideal for applications where running copper wires would be impractical
4. Due to the fibres being non-conductive, it can be used where electrical isolation is needed
5. The fibres are do not pose a threat to its surroundings, such as in a chemical plant where a spark could cause an explosion.
6. For security reasons, as it is very hard to tap into a fibre cable to read data signals.
http://en.wikipedia.org/wiki/Fiber-optic_communication (Fiber-optic communication - Wikipedia)
http://en.wikipedia.org/wiki/Total_internal_reflection (Total internal reflection - Wikipedia)
http://en.wikipedia.org/wiki/Optical_fiber (Optical Fiber - Wikipedia)
Advantages and Disadvantages:
http://csusap.csu.edu.au/~agarts01/advantages_and_disadvantages.html (Advantages and Disadvantages)
http://upload.wikimedia.org/wikipedia/commons/0/02/Optical_fiber_cable.jpg (Optical fiber cable image)
Done by: Tse Tzang, Christian, JingHeng
The fundamental physical phenomenon at work in the eye is that when light crosses a boundary between two media (such as air and the
eye's jelly), part of its energy is reflected, but part passes into the new medium. In the ray model of light, we describe the original ray as splitting into a reflected ray and a transmitted one (the one t
hat gets through the boundary). Of course the reflected ray goes in a direction that is different from that of the original one, according to the rules of reflection we have already studied. More surprisingly --- and this is the crucial point for making your eye focus light --- the transmitted ray is bent somewhat as well. This bending phenomenon is called refraction. The origin of the word is the same as that of the word “fracture,” i.e., the ray is bent or “broken.” (Keep in mind, however, that light rays are not physical objects that can really be “broken.”) Refraction occurs with all waves, not just light waves.
The actual anatomy of the eye, is quite complex, but in essence it is very much like every
other optical device based on refraction. The rays are bent when they pass through the front surface of the eye. Rays that enter farther from the central axis are bent more, with the result that an image is formed on the retina. There is only one slightly novel aspect of the situation. In most human-built optical devices, such as a movie projector, the light is bent as it passes into a lens, bent again as it reemerges, and then reaches a focus beyond the lens. In the eye, however, the “screen” is inside the eye, so the rays are only refracted once, on entering the jelly, and never emerge again.
A common misconception is that the “lens” of the eye is what does the focusing. All the transparent parts of the eye are made of fairly similar stuff, so the dramatic change in medium is when a ray crosses from the air into the eye (at the outside surface of the cornea). This is where nearly all the refraction takes place. The lens medium differs only slightly in its optical properties from the rest of the eye, so very little refraction occurs as light enters and exits the lens. The lens, whose shape is adjusted by muscles attached to it, is only meant for fine-tuning the focus to form images of near or far objects.
The ray model of light is very useful in explaining lenses.A lens is a piece of glass or any other transparent material with two curved surfaces, or with one curved and one flat surface. A convex lens is a lens that is thicker in the middle than at its edges. Refraction through such a lens causes parallel light rays to converge (meet) at a point called the principal focus. The lens of your eye is a double convex lens that focuses an image on the retina of the eye.
Wednesday, August 3, 2011
Abbe-Koenig "roof prism" design
The brilliance of diamond is due to total internal reflection. The critical angle of light traveling from diamond to air is 24.4 degrees.The ray of light entering the diamond (incident angle) fall at angle greater than 24.4 degrees. This results in multiple, total internal reflections at various angles and remains within the diamond. Hence diamond sparkles.
Endoscopes use fiber optics technique. A patient can swallow a tube containing a fine glass fiber through which a doctor can examine the internal stomach parts and hence unnecessary surgeries can be avoided. This is so as the optic fibres uses the principles of total internal reflection to transmit an image that can be inspected visually outside the body.
Advantage of using total internal reflection in endoscopes (or medical purposes):
- No operation will be needed to observe the internal organs of a patients
- Tumors in the body can be killed by using this theory. No operation is needed as the optical fibre rays can be reflected and aimed at the tumor for it to be killed.
Disadvantages of using total internal reflection in endoscopes:
- The equipment needed are expensive
- Total internal reflection might not occur when the angle of incidence is changed, thus causing the equipment unusable.
- Kang Yan
- Bing Jue
- Jun Peng
Friday, July 22, 2011
Please note that the powerpoint slides and additional practice questions are up.
Tuesday, July 19, 2011
Tuesday, July 12, 2011
D) Take 10 mins and complete the pre-quiz on the topic