Why Use Microscope Immersion Oil?

When light passes from a material of one refractive index to another (for example: from glass to air), it bends. When using the 100x oil immersion objective without immersion oil, light is being lost when it passes from the glass slide, through the air, to the glass objective lens. In short, the light is bending, resulting in a microscopy image that is less crisp and clear than if immersion oil were being used with that same lens.

Take a look at the example below - these images were captured using the UX1 Achromat microscope 100x oil immersion lens. The first image was captured dry, the second using microscope immersion oil.

Duodenum captured using a 100x achromat oil lens dry (without immersion oil).

Duodenum captured using a 100x achromat oil lens with immersion oil.

Visit this "Microscope Immersion Oil Explained" page to learn more about why, when and how to use immersion oil.