Concave Mirror

Concave mirror is a mirror with a surface shaped into lengkungna . On the mirror plane reflector ( shiny part ) is in arch .

Concave mirror that will be discussed is only a slice of a spherical shell . Thus , the center is also a ball that sliced ??the center of curvature mirror .

Figure II.4 Illustration concave mirror

                                              

Based II.4 image above , it can be defined some of the terms contained in a concave mirror as follows :

1. Point F is called the focal point or fire point mirror .
2. M point is called the center of curvature mirror .
3. The point O is called the center of the mirror field .
4. Line through the point O and M is called the major axis .
5. Distance OM = R is called the radius of curvature of the mirror .

Basically , the law of reflection of light on various surfaces is the same . Reflections distinguishing trait is the direction of the normal line . On a flat mirror all the normal line direction at every point in the same reflective plane ( parallel ) , which is perpendicular to the plane of reflection . While on a concave mirror , the direction all the normal line at any point on the reflected field is toward the center of curvature of the mirror . By using the law of refraction of light , we can see the reflection of any light beam toward the surface of the concave mirror .

Coming beam reflected on a concave mirror is always close to the main axis . In other words , the reflected rays of light which comes always collected . Because it is always collects the reflected light , the concave mirror is called converging mirror .

The reflected rays of parallel rays that come in a concave mirror intersect at one point . Point of intersection of the reflected rays lie on the major axis and is called the focal point of a concave mirror . Distance to the center focus point field mirror is half the length of the radius of curvature of the mirror . If R is the radius of curvature of the mirror and f is the focal distance of the central point of the mirror field , then apply :

R
f = .......................................... ( 2.6 )
2

As in the flat mirror , concave mirror images formed from the intersection of the reflected rays . To make it easier to paint shadows on the concave mirror , usually required special assistance rays in a concave mirror . Rays that include :

• a. Axis parallel to the incident light is reflected through the main focal point .

Figure II.5 reflection rays come parallel to the main axis of the concave mirror

               

• b . Rays coming through the focal point is reflected parallel major axis .

Figure II.6 reflection rays coming through the focal point of the concave mirror

               

• c . Rays coming through the center of curvature mirror reflected back through that point .

Figure II.7 reflection rays coming through the center of curvature on the concave mirror

        

Object distance , shadow distance and distance focal point on a concave mirror turns interrelated . If two of the three magnitude is known , then the third magnitude can be searched . Through careful experiments and performed repeatedly , the experts finally obtain third link these quantities as follows :

 1 1 1
 + = ................................. ( 2.7 )
So Si f
or ,
1 1 2
 + = ................................. ( 2.8 )
So Si R
Since R = 2f .

Description :
So = the distance from the object to the center of the mirror field .
Si = the distance from the shadow to the center of the mirror field .
R = the center of curvature mirror .
f = distance from the focal point to the center of the mirror field .

Because the shadow could be in front of a mirror or behind a mirror , it is used to distinguish the condition that for the shadow behind the mirror ( virtual image ) given a negative sign . If the calculation of distances obtained is negative shadow , the shadow formed illusory .

Concave mirror images size sometimes smaller or bigger than the size of the object . To determine whether the shadow of an object larger or smaller than the object , the magnification is defined shadows . Magnification of the shadow of states comparison between high- and high object shadow or the ratio between the distance of the shadow and object distance . If given the symbol M , magnification of the shadow can be expressed by the following equation :

- The hi
 M == ....................................... ( 2.9 )
 so ho

Description :
So = the distance from the object to the center of the mirror field .
Si = the distance from the shadow to the center of the mirror field .
ho = height of objects .
hi = high shadows .
M = magnification of objects .

Many areas of everyday life that make use of a concave mirror , both the simple and the application of advanced technology . Some of the benefits of a concave mirror is as follows :

• a. Concave mirror can be used to collect light energy to have great power . In addition, the concave mirror can also be used to collect sound waves , heat radiation , and the TV signal . Nature of the concave mirror to collect this wave is applied to the satellite , oven light , telescopes and radar receivers .
• b . Concave mirror can be used to align the beam of light coming from the lamp and projector flashlights like the movie theaters .
• c . Concave mirror can be used to enlarge the shadow , for example, to make up or shave . You do this by placing objects between the focus and the center of the mirror field . The thought behind the mirror and magnified illusory .

Figure II.8 Examples of the formation of a concave mirror images