Rearview+Mirror

= Rear-view Mirrors =

Main

Timeline:
media type="custom" key="6286419" 1911 - At the first Indy 500 in 1911, race winner Ray Harroun’s car used a device for the first time that has since become standard equipment on all cars – the rear-view mirror. 1968 - Rear-view Mirrors become required by law 1993 - The Federal Government revised the requirements on school buses

General Information:
Rear-View Mirrors were invented in order to reduce the number of accidents and injuries caused by accidents where the driver cannot or has a hard time seeing vehicles or other objects behind the vehicle. The rear-view mirror made its debut at the Indy 500 in 1911, according to Yahoo Sports, and by 1968 it became a required safety device in cars.

Legislation:
As of January 1, 1968, the Federal Government required all cars, trucks, buses, etc. to be equipped with rear-view mirrors.

In 1993, the Federal government revised the standards for school buses.

**Rearview Mirrors Most modern day cars come equipped with three rearview mirrors. One center mounted and one on each front door. The purpose of rearview mirrors is to allow the driver to see behind the car without actually having to turn around. From a safety standpoint they allow the driver to keep his/her eyes on the road and still see other drivers behind them. ** The center mounted mirror is a simple flat mirror that produces an image with the same magnification as the original object. With a magnification of one the virtual image in the mirror appears to be the same distance behind the mirror as the object is in front of the mirror. This allows the driver to accurately judge the distance between them and the object. Along with accurately depicting the distance of the object, the center mounted rearview mirror also accurately portrays its size as one magnification means that the object height is the same height as the virtual image. ** Both of the side mounted rearview mirrors on automobiles are convex mirrors. Convex mirrors have a magnification less than one, and produce a virtual image. This image is upright and appears smaller in the mirror. So why use convex mirrors if their virtual images are not accurate representations of the objects? Well, convex mirrors provide a larger viewing angle than simple flat mirrors, this creates much smaller blind spots for the vehicle operator. In addition to this bonus, side mounted rearview mirrors on cars have very small radii of curvature and therefore cause minimal distortion in their virtual images. Some distortion is present and that’s why nearly every side mounted rearview mirror has a warning “Objects in mirror are closer than they appear.” **
 * Center Mounted Rearview Mirror
 * Side Mounted Rearview Mirrors

This equation relates the radius of curvature to the focal length of a convex/concave mirror. In the case of rearview mirrors the convex application is needed. In most cars the radius of curvature is small resulting in a small focal length. This equation is used to determine either the object or virtual image’s distance from a convex mirror using the focal length. This equation can mathematically determine what the brain interprets while using convex side mounted rearview mirrors. This equation models magnification. Magnification is really just a ratio of image size/distance from the mirror to object size/distance from the mirror. Side mounted rearview mirrors have a magnification less than one but not by much, so images in the side mounted rearview mirrors are just slightly closer than the appear. The magnification of the flat center mounted rearview mirror is exactly one as the object and virtual image are the same size and distance from the mirror [|http://commons.wikimedia.org/w/index.php?title=Special%3ASearch&search=convex+mirror&fulltext=1]
 * Important Equations for Rearview Mirrors**

The above ray diagram shows what is really going on with the convex mirrors used in cars. As the diagram shows the object appears to be much larger than the image suggesting a large magnification. This is due to the large radius of curvature of the mirror in the diagram

**Connection:**

Again, the government stepped in because mirrors keep people safer while on the roads. Mirrors allow drivers to see behind them and beside them while still keeping an eye on the road ahead. Mandating the use of mirrors keeps everyone safer while on the roads.

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