Convex Lens

The main characteristic of a convex lens is the center of the lens is thicker than the edges . Often called a convex lens convex lens or positive lens. The following are the types of convex lens surface by a curved shape :

• Bikonveks lens is a lens that has two convex surfaces .
• Plan - convex lens is a lens that has a convex surface and a flat surface .
• Convex - concave lens is a lens that has one convex and one concave surface . In this case , the convex surface is more dominant than the concave surfac .

Convex lens is to collect light, so it is also called a converging lens. Point where the gathering is called refraction of light parallel to the focal point of the lens. Because the focal point of a convex lens can be captured, then the focal point of the convex lens is real or true. Distance to the focal point of the lens is called the focal point distance focal distance. Convex lens has two focal points are equidistant from the center of the lens. Focus distance of each lens varies depending on the combination of both surface curvature.

Because light can come from the front or from behind the lens , to make it easier to determine its shadow , the part where the lens is refracted rays come forward and set up as part of the lens where light is refracted set as the back . Focus in front of the lens is called the focal point (F1) and the other focal point is called the focus back (F2).

Figure II.15 Illustration Convex Lens

                                                

As with mirrors, the lenses are also three special rays are refracted by the lens. To discuss the light it needs to be known a convex lens term.

1. Line AB is called the main axis of the lens .
2. Point O called the point of the optical lens .
3. F1 is the focal point of the front and back of the F2 is the focal point .

Special rays and refraction properties of the convex lens is as follows :

• a. Axis parallel to the incident light is refracted through the main focal point of the back .

Figure II.16 Refraction rays that come in parallel to the main axis convex lens

                        

• b . Rays coming through the front focal point refracts parallel to the main axis .

Figure II.17 Refraction rays coming through the focal point on convex lens

                             

• c . The rays coming through the optical center passed without refracted .

Figure II.18 Refraction rays coming through the optical center of the convex lens

                      

Equations involving convex lens focal distance, object distance, and the distance like a shadow on a concave mirror, namely :

1 1 1
 + = ................................. ( 2.13)
So Si f
- The hi
 M == .............................. ( 2.14)
 so ho

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

As well as a concave mirror , focal length of a convex lens is positive because it is the real focus of the convex lens . Real object sits in its front lens and the calculation is positive . Virtual object is located behind the lens and in the calculation is negative. Real image located behind the lens and in the calculation is positive. Virtual image is located in front of the lens and the calculations are negative .

Properties of convex lenses that collect light and shadow can enlarge widely used in various devices , such as :

1. Magnifying glass .
2. Microscope .
3. Glasses .
4. Camera .
5. Binoculars .

Figure II.19 Examples of shadow formation in a convex lens