fiber optics.
Friday, August 10, 2007
7:05 AM
Fiber Optics is a technology that uses specially designed bundles of transparent fibers to transmit light.
An optical fiber has
three main parts:
- Core - The glass center of the optic fiber where light is transmitted.
- Cladding - This material surrounds the core and functions to reflect the light back to the core.
- Buffer coating - A protective coating made from plastic that repels damage and moisture.
Two types of optical fibers are present.
Single-mode Optical fiber An optical fiber with a core diameter of less than 10 microns. Used for high-speed transmission over long distances, it provides greater bandwidth than multimode, but its smaller core makes it more difficult to couple the light source. Increasingly, singlemode fiber is used for shorter distances.
Multimode optical fiber An optical fiber with a larger core than singlemode fiber. It is the most commonly used fiber for short distances such as LANs. Light can enter the core at different angles, making it easier to connect the light source to broader light sources such as LEDs.
How exactly do they work?
Light travels by internal reflection. Imagine that the optical fiber is bent, how does light travel? Light from the core is constantly reflected by the cladding (as mentioned above).
the camera and the eye
6:48 AM
| Similarities |
| 1. | opening for light to enter | aperture | pupil |
| 2. | control the amount of light entering camera/eye | diaphragm control size of aperture | iris muscles control size of pupil |
| 3. | refract light | glass biconvex lens | mainly cornea ;
lens, aqueous & vitreous humor |
| 4. | object of light action to form image | photosensitive chemicals on film | photoreceptors(rods & cones) in retina |
| 5. | absorb excessive light to prevent multiple images formation | dark internal surface | pigmented, dark choroid |
| Difference |
| 1. | focusing mechanism | change distance between lens & film | change focal length of lens using ciliary muscles |
SOURCE: http://library.thinkquest.org/28030/eyeevo.htm
LENSES.
4:14 AM
RAY DIAGRAM FOR CONVERGING LENSES:- The first incident ray is a parallel line from the tip of the object to the lens.
- The second incident ray passes through the intersection of both axes from the tip of the object.
- The third incident ray passes through the focal point in front of the lens from the tip of the object.
- From the point where the incident ray touches the lens, draw a line towards the focal point at the backside of the lens.
- The second incident ray passes up to the back of the lens.
- From the tip of the third incident ray, draw a parallel line.
- From the point where the three extended rays meet, draw a perpendicular line and you have formed your image.
RAY DIAGRAM FOR DIVERGING LENSES:- Draw a parallel line from the tip to the lens for your first incident ray.
- From the tip of the object, draw a line to the intersection of both axes for the second incident ray.
- The third incident ray passes trough the focal point at the back of the lens from the tip of the given object.
- Given the focal point in front of the lens and the point where the first incident ray touches the lens, draw a line passing through both points.
- Draw a line parallel to the main axis from the point where the second incident ray touches the lens.
- Then, extend the third incident ray.
- From the point where the three extended rays meet, draw a perpendicular line and there you have it, your image!
