why is oil necessary when using the 100x objective

From the above it is understood that oil between the specimen and the objective lens improves the resolving power by a factor 1/ n. Objectives specifically designed for this purpose are known as oil immersion objectives. Oil immersion objectives are used only at very large magnifications that require high resolving power. Objectives with high power magnification have short, facilitating the use of oil. The oil is applied to the specimen (conventional microscope), and the stage is raised, immersing the objective in oil. (In
the oil is applied to the objective).


The refractive indices of the oil and of the glass in the first lens element are nearly the same, which means that the refraction of light will be small upon entering the lens (the oil and glass are optically very similar). The correct immersion oil for an objective lens has to be used to ensure that the closely. Use of an oil immersion lens with the incorrect immersion oil, or without immersion oil altogether, will suffer from spherical aberration. The strength of this effect depends on the size of the refractive index mismatch. Oil immersion can generally only be used on rigidly mounted specimens otherwise the of the oil can move the coverslip and so move the sample underneath.


This can also happen on inverted microscopes because the coverslip is below the slide. It is all about the refraction. When light changes the medium from which it passes, it changes the path. In microscopy the light is reflected by the mirror,. It is all about the refraction. When light changes the medium from which it passes, it changes the path. In microscopy the light is reflected by the mirror, condensed by condenser, restricted by the diaphragm, enters the glass slide on which the object to be seen is lying.


The object must be transparent. At this stage the light takes up the image. Next it comes into light medium and then enters into glass medium of the lens of objective lens. This change in medium distorts the path of light. If the magnification is low. The distortion does not matter much. When we are using 100x objective, magnification is 1000 times. Here it matters. We wish to see the morphology correctly. Boundaries make size, overlying details disturb the study.


So distortion is to be avoided. We put a drop of oil on the object and touch the 100x objective to it, in short we immerse the objective in oil, so it is known as oil immersion lens. Now the light takes up transparent image, comes into oil, goes to objective lens. Medium changes but light path do not change because the reported refractory index of the oil used is 1. 5 and it is equal to glass. So the light is not distorted. By avoiding distorted light we can have sharp bright image and study the morphology of the cell perfectly. Thanks and best wishes.

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