refractive index of the solid immersion lens n3 refractive index As a second benchmark a high numeric aperture oil objective is chosen which GetPDFServlet?filetype=pdf&id=JAPIAU&idtype= cvips&prog. reconfigured as a variable numerical aperture microscope condenser by depositing a inner edge of the top aperture of the metal cage of the oil- immersion objective lens Sorry, there is no online preview for this file type. Diffraction: “light waves change direction when passing through an opening or some microscope objectives use oil (n = for immersion oil) to increase the n Numerical Aperture is a way to define the cone angle of light which passes .

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In light microscopyoil immersion is a technique used to increase the resolving power of a microscope. This is achieved by immersing both the objective lens and the specimen in a transparent oil of high refractive index apertuge, thereby increasing the numerical aaperture of the objective lens. Immersion oils are transparent oils that have specific optical and viscosity characteristics necessary for use in microscopy.

Typical oils used have an index of refraction around 1.

Immersion Oil and Refractive Index | MicroscopyU

Many condensers also give optimal resolution when the condenser lens is immersed in oil. Lenses reconstruct the light scattered by an object. To successfully achieve this end, ideally, all the diffraction orders have to be collected.

This is related to the opening angle of the lens and its refractive index. The resolution of a microscope is defined as the minimum separation needed between two objects under examination in order for the microscope to discern them as separate objects. A measure of the resolving power, R. State of the art objectives can have a numerical aperture of up to numfrical.


If the space between the objective lens and the specimen is filled with oil however, the numerical aperture can obtain values greater than unity. This is because oil has a refractive index greater than 1.

Objectives specifically designed for this purpose are known as oil immersion objectives. Oil immersion objectives are used immersiion at very large magnifications that require high resolving power. Objectives with high power magnification have short focal lengthsfacilitating the use of oil.

The oil is applied to the specimen conventional microscopeand the stage is raised, immersing the objective in oil.

In inverted microscopes the oil filetypw 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.

Oil immersion

The correct immersion oil for an objective lens has to be used to ensure that the refractive indices match 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 surface tension 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. Before the development of synthetic immersion oils in the s, cedar tree oil was widely used. Cedar oil has an index of refraction of approximately 1. The numerical aperture of cedar tree oil objectives is generally around 1. Cedar oil has a number of disadvantages however: Cedar oil must be removed from the objective immediately after use before it can harden, since removing hardened cedar oil can damage the lens.

In modern microscopy synthetic immersion oils are more commonly used, as they eliminate most of these problems. Unlike natural oils synthetic ones do not harden on the lens and can typically be left on the objective for months at a time. From Wikipedia, the free encyclopedia.

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