The objective lenses of compound microscopes are parfocal. You do not need to refocus (except for fine adjustment) when switching to a higher power if the object is in focus on a lower power. The field of view is widest on the lowest power objective. When you switch to a higher power, the field of view is closes in.
ᕼOᑭᗴ ᑎᗩKᗩTᑌᒪOᑎᘜ ☯︎ᴥ︎︎︎☯︎
