Final answer:
Oil immersion objective lenses are used in microscopy to improve resolution by filling the space between the specimen and the lens with oil, which increases the light collected.
Step-by-step explanation:
The use of oil immersion objective lens is essential in microscopy when observing specimens at very high magnifications.
When light passes through the small amount of air between the specimen and the lens, the difference in refractive indices of air and glass causes the light to scatter before it can be focused by the lens, compromising resolution.
To solve this problem, oil with a similar refractive index to glass is used to fill the space between the specimen and the lens, allowing more light to be collected and increasing resolution.