Physics 59 Optical Instruments (12 of 20) Why Are Oil Drops Used for Microscopes?

From a channel Lumen includes in full: Michel van Biezen (a physics instructor) has thousands of short worked lessons in physics, maths, chemistry and astronomy, organised by topic and course.

A 4-minute video from Michel van Biezen's catalogue; the title names its topic.

Video by Michel van Biezen, played through YouTube's embedded player.