Why should the oil immersion objective be cleaned immediately after use?

Answer 1

because it needs to be keep cleaned all the time to avoid accumulation of dirt which eventually can affect resolution of lense...hope this helps!!!

Also go through following site also...its would be useful for you to understand more on oil immersion lens.

http://www.microscopy-uk.org.uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/mag/artmar02/pjoil.html

Answer 2

Clean with a soft wipe after each use. Doesn't take much, and cover the scope when not in use to avoid dust buildup .