The proper use of a collimating screw in a light microscope
Adjusting the focus using the collimating screw to find the object can be said to be the most important step in the use of the microscope, and it is also the step that students find most difficult. Students are very likely to make the following mistakes: first, directly adjusting the focus under high magnification; second, always looking at the field of view in the eyepiece regardless of whether the barrel is rising or falling; third, not understanding the critical value of the object distance, the object distance is adjusted to 2-3 cm when still adjusting upward, and turning the focusing helix very quickly. The results of the first two errors often result in the objective lens touching the mount and damaging the mount or lens, while the third error is one of the most common phenomena when students use microscopes. In response to the above errors, teachers must emphasise to students, adjust the focus must be adjusted at low magnification, first turn the coarse focusing spiral, so that the barrel of the microscope slowly down, the objective lens close to the slide, but be careful not to let the objective lens touch the slide, in the process of the eye from the side of the objective lens, and then use the left eye towards the eyepiece to gaze at the eyepiece, and slowly reverse the adjustment of the coarse focusing spiral, the barrel of the microscope to slowly rise until the object is seen until the object image, and so on. At the same time, explain to the students that the general microscope object distance in about 1 cm, so if the object distance has been far more than 1 cm, but still do not see the object image, it may be that the specimen is not in the field of view or turn the coarse focusing spiral too fast, at this time, should be adjusted to the position of the mount, and then repeat the above steps, when there is a fuzzy object in the field of view, it is necessary to switch to a fine focusing spiral adjustments, only in this way can we narrow down the scope of the search to improve the speed to find the Only in this way can the search range be narrowed and the speed of finding the object be improved.
What is the meaning of 10/0.25 on the objective lens of a microscope?
10 is the magnification of the objective lens and 0.25 is the numerical aperture of the objective lens. \x0d\x0a The numerical aperture of the objective lens (N.A=n.sinu) is the main parameter that determines the discriminatory rate (1/d) of the microscope, and the larger the value, the higher the discriminatory rate - i.e., the higher the ability to discriminate between fine targets. Therefore, the discriminating rate of a microscope is directly proportional to the numerical aperture of the objective lens and inversely proportional to the wavelength of the illuminating light. \x0d\x0a It should be noted that the discriminatory rate of a microscope is not the same thing as the magnification, just as the target is enlarged, but not necessarily look clear; only when the objective lens discriminatory rate is high, the details of the target can be clearly distinguished. \x0d\x0a The vertical discrimination of a microscope is also known as the depth of field; this is not unfamiliar to those who have used a camera. \x0d\x0a The discriminating power of a microscope is related only to the objective lens and not to the eyepiece; the eyepiece acts only as a magnifier. Therefore, the objective lens is an important part of the microscope.
