What is immersion oil used for and what is the proper technique for using it?
Compound microscope objectives in the 90X to 100X range require immersion oil. Background The upper limit of the resolving power of light microscopes is slightly above 1000X. Objectives of 90 to 100X, when coupled with a 10X eyepiece, approach that upper limit. Even in the range of 900 to 1000X, a clear image is only possible if every bit of available light is directed through the microscope optics to the viewer’s eye. Immersion oils play an essential role in maximizing the amount of light producing the image the viewer sees. In the airspace between the slide and the objective lens, light is refracted, scattered, and effectively lost. This happens because the refractive index of air (approximately 1.0) is very different from that of glass (approximately 1.5), and light passing through a glass/air interface is refracted (bent) to a large degree. By reducing the amount of refraction at this point, more of the light passing through the slide will be directed to the very narrow diameter le
