Question

Which microscope lens requires oil immersion? Why is the oil immersion necessary when viewing certain cellular structures? Please explain.

Answer 1

Oil is always added in the objectives of the microscope which holds the objective lens.

Resolving power of the microscope is directly proportional to the wavelength of the light and inversely proportional to the numerical aperture. Smaller the numerical aperture of the microscope, higher will be the resolving power. Numerical aperture of the microscope is directly proportional to the refractive index of the medium. Higher the refractive index, higher will be the numerical aperture and lower will be the resolving power.

Lower resolving power means that the microscope is able to resolve two closely placed objects at that minimum distance as as two different objects. So lower resolving power of a microscope is better than higher resolving power. (RP of 0.2 um is lower and better than RP of 2 um).

We require oil immersion microscope to see cellular structures or organelles like mitochondria, chloroplast or vacuoles are lysosomes. This is because these are very small organelles and are closely placed to each other. If we use oil immersion microscope, then they will appear as separated organelles and we would be able to see some internal details as well.

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