The optical power of a lens shows, how strongly beams in it refract. Depends on it as far as the image will be enlarged. Practically on all lenses their optical power is specified. If there is no such information, it is possible to define this value independently.
It is required to you
- - optical lens;
- - light source;
- - screen;
- - ruler not less than 40 cm long.
Instruction
1. At first it is necessary to measure focal length of a lens. In this case at first fix a lens in vertical position in front of the screen, and then direct to it light beams directly through the center of a lens. It is important to get precisely a light beam to the center, otherwise results will be doubtful.
2. Now install the screen at such distance from a lens that the beams leaving it gathered in one point. By means of a ruler it is necessary only to measure the received distance – apply a ruler to the center of a lens and define distance in centimeters to the screen.
3. Further the value needs to be transferred to meters. Now you without effort determine the optical power of a lens. It will be equal to the relation 1/1 to focal length.
4. If you cannot define focal length, it is worth using one more checked way – the equation of a thin lens. To find all working-out equations, it is necessary to experiment with a lens and the screen.
5. Establish a lens between the screen and a lamp on a support. Move a lamp and a lens so that finally on the screen the image turned out. Now measure by a line of distance: - from a subject to a lens; - from a lens to the image. Transfer results to meters.
6. Now it is possible to count optical power. At first it is necessary to divide number 1 into the first distance, and then and into the second received value. Summarize the received results - it is and there will be an optical power of a lens.
7. Remember that it is measured in dioptries and can be both positive, and negative. The negative value turns out in case of the disseminating lens. Then in a formula it is necessary to put the sign "minus".