Cell structure: explain question

A student uses a light microscope with an eyepiece graticule and a stage micrometer. The stage micrometer has 100 divisions in 1 mm. The student aligns the graticule and micrometer and finds that 50 graticule divisions correspond to 80 divisions on the stage micrometer. The student then observes a stained preparation of human cheek cells and sees mitochondria as small rods. (a) Define the terms resolution and magnification. (b) Explain how the student can use the calibration to determine the actual length of a mitochondrion. (c) Explain why, even with accurate measurement, the light microscope cannot reveal the detailed internal structure of mitochondria, and state how electron microscopy would provide more detail.