Why Immersion Oil Is Used in Microscopy?

Immersion oil increases the resolving power of the microscope by replacing the air gap between the immersion objective lens and cover glass with a high refractive index medium and reducing light refraction.

Why is immersion oil used in 100x objective?

The 100x lens is immersed in a drop of oil placed on the slide in order to eliminate any air gaps and lossof light due to refraction (bending of the light) as the light passes from glass (slide) → air →​​​​​​​ glass (objective lens).

Why oil immersion is used in microscope?

In light microscopy, oil 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, thereby increasing the numerical aperture of the objective lens.