Why is oil necessary when using the 90x to 100x objective?

Answer 1

The oil immersion fills the space between the objective and the specimen and matches the refractive index of the glass coverslip and glass objective lens. At a given focal length, this allows you to acheive a greater numerical aperature (better light collection efficiency, better resolution).

Answer 2

An oil immersion objective allows for higher resolution at high magnification in optical microscopes. The refractive index of the oil is higher than air allowing the objective lens to have a numerical aperture as high as 1.6 (although the aperture is usually less than this but still greater than 1) so that the light is transmitted from the specimen to the outer face of the objective lens with minimal refraction. The larger numerical aperture allows collection of more light making detailed observation of smaller details possible.

Answer 3

Oil immersion is necessary when using high magnification objectives (90x to 100x) to reduce the refraction of light as it passes through the specimen, helping to improve resolution and clarity of the image. Due to the high magnification, the light needs to pass through the specimen more effectively, which is achieved by using oil with a refractive index that closely matches that of glass.

Answer 4

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