COMPARISON OF A HUMAN EYE TO A CAMERA
this is one of the must-post topics so here it goes...
(Pretty much the same with the website but I thoroughly read it (>_<("') )
HUMAN EYES vs. CAMERA
Human eyes have often been compared to cameras. They are alike in terms of structure, but they have one fundamental difference in functioning mechanism.
DIAGRAM From ://library.thinkquest.org/28030/media/evocam5.gif
THE RAY METHOD
THE RAY METHOD
I know all you people out there are familiar with this so I didn't include more elaborate things to point out, I'll just post this. ("')(>_<)("')
| Images formed by a converging spherical mirror | ||
|---|---|---|
| | | Characteristics of the Image |
| a) Distant object |  | Real Inverted Smaller than object At F |
| b) Object beyond C |  | Real Inverted Smaller Between C and F |
| c) Object at C |  | Real Inverted Same size as object At C |
| d) Object between F and V |  | Virtual Erect Larger than object Behind mirror |
| e) Object at F |  | No image Reflected rays are parallel |
| Images formed by a diverging spherical mirror | ||
| e) Object at F |  | Characteristics of the image regardless of object postion Virtual Erect Smaller than object Behind mirror between F and V |
THE RAY METHOD
I know all you people out there are familiar with this so I didn't include more elaborate things to point out, I'll just post this. ("')(>_<)("')
| Images formed by a converging spherical mirror | ||
|---|---|---|
| | | Characteristics of the Image |
| a) Distant object | | Real Inverted Smaller than object At F |
| b) Object beyond C | | Real Inverted Smaller Between C and F |
| c) Object at C | | Real Inverted Same size as object At C |
| d) Object between F and V | | Virtual Erect Larger than object Behind mirror |
| e) Object at F | | No image Reflected rays are parallel |
| Images formed by a diverging spherical mirror | ||
| e) Object at F | | Characteristics of the image regardless of object postion Virtual Erect Smaller than object Behind mirror between F and V |
Fibuh Optiks
Fiber optics
•(optical fibers) are long, thin strands of very pure glass about the diameter of a human hair. They are arranged in bundles called optical cables and used to transmit light signals over long distances.
 Parts of a single optical fiber |
If you look closely at a single optical fiber, you will see that it has the following parts:
- Core - Thin glass center of the fiber where the light travels
- Cladding - Outer optical material surrounding the core that reflects the light back into the core
- Buffer coating - Plastic coating that protects the fiber from damage and moisture
Optical fibers come in two types:
- Single-mode fibers
- Multi-mode fibers
Single-mode fibers have small cores (about 3.5 x 10-4 inches or 9 microns in diameter) and transmit infrared laser light (wavelength = 1,300 to 1,550 nanometers). Multi-mode fibers have larger cores (about 2.5 x 10-3 inches or 62.5 microns in diameter) and transmit infrared light (wavelength = 850 to 1,300 nm) from light-emitting-diodes (LEDs).
Some optical fibers can be made from plastic. These fibers have a large core (0.04 inches or 1 mm diameter) and transmit visible red light (wavelength = 650 nm) from LEDs.
How Does an Optical
Fiber Transmit Light?
Suppose you want to shine a flashlight beam down a long, straight hallway. Just point the beam straight down the hallway -- light travels in straight lines, so it is no problem. What if the hallway has a bend in it? You could place a mirror at the bend to reflect the light beam around the corner. What if the hallway is very winding with multiple bends? You might line the walls with mirrors and angle the beam so that it bounces from side-to-side all along the hallway. This is exactly what happens in an optical fiber.
Diagram of total internal reflection in an optical fiber
THAT'S ALL FOLKS!!!
Refraction- The bending of light as it moves from one substance to another.
Ask students for any more examples they can think of where refraction takes place? After students start into different kinds of lenses start with this... Then, start on how lenses, a piece of material which light is able to pass through, are used to refract light. Also, explain that there are different types of lenses.
•Convex
•Concave
Convex - A lens which is thicker in the middle than on the ends.
Concave - A lens which is thinner in the middle than on the ends.
A MINI DIAGRAM OF MINE
Convex Lenses Characteristics:
•Refracts parallel light rays so they come together at a single point. Does anyone know what it is called when the light rays are made to come together?
-Known as convergence.
•Point is known as focal point.
•Distance from center of lens to focal point = focal length.
•The thicker the middle of the lens the shorter the focal length.
•Example of a convex lens is a magnifier.
•Image can be seen without actually looking through the lens. This type of image is known as a real image.
•When held close to objects, inside of its focal length, it produces an image known as a virtual image. To see a virtual image you must look through the lens.
Concave Lenses Characteristics:
•Refracts the rays so they come apart. . Does anyone know what it is called when the light rays are made to come apart from each other?
-Known as divergence.
•Always forms a virtual image.