Question

what is the purpose of using oil for the oil immersion process?

Explanation:

Oil has a higher refractive index than air. When using an oil immersion objective lens, placing oil between the lens and the specimen reduces light refraction at the air - glass interface. This allows more light to enter the objective lens, resulting in a brighter and higher - resolution image.

Answer:

To reduce light refraction (increase light collection), resulting in a brighter and higher - resolution image.