A New Method for Measuring Microscope Magnification
The measurement of the magnification of the microscope is a basic experiment in university physics experiments. The magnification of the microscope M = the magnification of the eyepiece × the magnification of the objective lens. The traditional method of measuring the magnification of the microscope is to use the direct observation method. This method is simple and intuitive , monotonous, but the accuracy of the reading is low, resulting in a large error. In view of this, this paper proposes a new method for measuring the magnification of the microscope, which greatly improves the accuracy of the experimental results.
Experimental principle
Use a collimator to measure the optical path of the focal length of the lens. Adjust the reticle engraved with five groups (called the Poirot plate) to the focal plane of the objective lens of the objective lens L0, remove the plane mirror, and place the focal length to be measured in front of the collimator If the lens is used, the image of the Poirot plate will be obtained on the image square focal plane F' of the lens to be tested.
Using the above experimental principles, after many experiments in the long-term teaching process, it is found that the collimator can be used to accurately measure the focal length of the objective lens of the microscope, the eyepiece, and the distance from the focal point of the eyepiece object to the field lens of the eyepiece, and then use a micrometer to accurately measure the microscope. The distance between the middle objective lens and the middle sight mirror of the eyepiece, the distance between the middle field mirror of the eyepiece and the sight mirror, and the optical interval between the objective lens and the eyepiece of the microscope can be calculated to obtain the focus of the compound optical train composed of the objective lens and the eyepiece. If the whole microscope is regarded as A simple magnifying glass .
Key steps in experimental system adjustment
(1) Adjust the collimation tube, that is, the reticle is strictly on the focal plane of the objective lens, so that the center of the reticle coincides with the optical axis of the collimation tube.
(2) Place the instrument on the optical bench and adjust to make the whole system coaxial.
(3) Measure the focal length of the objective lens in the microscope (taking the Boro plate of the collimator as the object), and move the objective lens axially until a clear image on the Boro plate is seen from the moving microscope, and the distance on the Boro plate is measured as The image distance of the second line of y is y' object, then the focal length of the microscope objective lens is:
(4) Measure the focal length of the object in the eyepiece of the microscope f, the distance from the focal point of the object in the eyepiece to the field mirror of the eyepiece, place the instrument on the optical bench, and adjust to make the whole system coaxial.
Align the viewing mirror in the microscope eyepiece to the collimator, and move the eyepiece axially until a clear image of the engraved line on the Borot plate is seen from the moving microscope, (F is the virtual focus, located between the viewing mirror and the field lens space) record the position of the eyepiece as x1; measure the distance y′ between the images of the two lines with a distance of y on the Boro plate
Compared with the new method in this paper, the traditional method of measuring the magnification of the microscope has the advantages of being simple, intuitive and clear at a glance. However, through the experiment, students cannot really understand the structure of each part of the microscope, especially the structure and principle of the eyepiece. The new experimental method allows students to personally experience the process of solving practical problems with the knowledge and skills of using the collimation method to measure the focal length of the lens; Really master the measurement method of the base point and focal length of the optical system, understand the specific application of the optical system in real life; enable students to learn to analyze from different angles and use different methods to solve the same problem. Because of the use of new methods, the original simple The observation experiment has become a comprehensive experiment with strong hands-on ability, rich content, and a combination of various experimental contents, and the experimental results show that the error is significantly reduced.
