## السبت، 21 مايو، 2011

### Curved Mirror

Curved Mirror

curved mirror is a mirror with a curved reflective surface, which may be either convex (bulging outward) or concave (bulging inward). Most curved mirrors have surfaces that are shaped like part of a sphere, but other shapes are sometimes used in optical devices. The most common non-spherical type are parabolic reflectors, found in optical devices such as reflecting telescopes that need to image distant objects, since spherical mirror systems suffer from spherical aberration.

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# Concave Mirror

A concave mirror, or converging mirror, is a curved mirror that bulges inward(away from the incident light). Concave mirrors reflect light inward to one focal point, therefore they are used to focus light. Concave mirrors show different image types depending on the distance between the object and the mirror. These mirrors are called “converging” because they tend to collect light that falls on them, refocusing parallel incoming rays toward a focus. This is because the light is reflected at different angles, since the normal to the surface differs with each spot on the mirror.

The image location and size can also be found by graphical ray tracing. A ray drawn from the top of the object to the surface vertex(where the optical axis meets the mirror) will form an angle with that axis. The reflected ray has the same angle to the axis, but is below it. A second ray can be drawn from the top of the object passing through the focal point and reflecting off the mirror at a point somewhere below the optical axis. This ray will be reflected from the mirror parallel to the optical axis. The point at which the two rays meet is the image point corresponding to the top of the object. Its distance from the axis defines the height of the image, and its location along the axis is the image location. The mirror equation and magnification equation can be derived geometrically from these two rays.
Uses
The unique reflection that is created by a concave mirror makes the device extremely helpful with a number of different devices. One of the most common applications is with the production of automobile headlights. By placing the source of light at the center of the concave mirror reflector, the result is a parallel beam of light that provides both plenty of visibility for the driver of the vehicle as well as points of light that are apparent to approaching vehicles.
The dental profession also benefits from the use of the concave mirror. The device is used to focus light onto the area of the mouth that the dentist is working with, providing a clear reflection of the tooth or set of teeth. The concave mirror is used in both hand held equipment as well as mirrors that can be mounted over the dental chair.

Images

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# Convex Mirror

A convex mirror is a spherical reflecting surface (or any reflecting surface fashioned into a portion of a sphere) in which its bulging side faces the source of light. Automobile enthusiasts often call it a fish eye mirror while other physics texts refer to it as a diverging mirror. The term “diverging mirror” is based on this mirror’s behavior of making rays diverge upon reflection. So when you direct a beam of light on a convex mirror, the mirror will allow the initially parallel rays that make up the beam to diverge after striking the reflective surface.
Uses

Since convex mirrors have wider fields of view than other reflective surfaces, such as plane mirrors or concave mirrors, they are commonly used in automobile side mirrors. Having a fish eye on your automobile will allow you to see more of your rear. A convex mirror is also a good security device. Store owners, for instance, install a number of them inside their stores and orient them in such a way that a single security personnel can see large portions of the store even while monitoring from a single location. They are the large disk-like reflective surfaces that you see near the ceilings of grocery or convenience shops. The same kind of security devices are installed on automated teller machines to give the person withdrawing a good view of what is happening behind him. Some cell phones are also equipped with these mirrors to aid users when performing a self portrait shot.
Images

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Mirror equation and magnification

The Gaussian mirror equation relates the object distance (do) and image distances (di) to the focal length (f):
$\frac{1}{d_\mathrm{o}}+ \frac{1}{d_\mathrm{i}} = \frac{1}{f}$.
The magnification of a mirror is defined as the height of the image divided by the height of the object:
$m \equiv \frac{h_\mathrm{i}}{h_\mathrm{o}} = - \frac{d_\mathrm{i}}{d_\mathrm{o}}$.
The negative sign in this equation is used as a convention. By convention, if the magnification is positive, the image is upright. If the magnification is negative, the image is inverted (upside down).
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Done By

1- Khalid Mahdi Al-Kathiri

Section 12.07