The primary role of the apertures in an electron microscope is to direct paraxial electrons back towards the column axis. True False The focal length of an electromagnetic lens depends on which of the following? Select all that apply. Accelerating voltage of the microscope Speed of the electron beam Current passing through the lens Electron wavelength None of these contribute. Which of the following are desired properties of an EM Grid? Select all that apply. Possess structural integrity to support thin films Stable in the electron beam Automatically wick the sample prior to blotting Chemically inert Well-defined spatial relationship between different areas of the grid Made of copper to conduct heat better