Can mitochondria be seen with the light microscope?

The best answer to this question is "it depends." It depends on the magnification power of the light microscope and the size of the mitochondria that you are trying to look at. Mitochondria can vary greatly in size. As a result, only the largest mitochondria can be seen with the highest magnification of light microscopes. A light microscope can magnify an image up to 400 times, and the limit of its resolution is about .2 microns. This is enough magnification power and resolution to examine larger mitochondria and things like lysosomes, nucleuses, and large vacuoles, but to examine the smaller examples, you will need something like an electron microscope. The magnification of those microscopes is up to 500,000 times and provides resolution down to 1 nanometer.
http://medcell.med.yale.edu/histology/cell_lab.php

https://www.sciencelearn.org.nz/images/534-mitochondria-under-the-microscope