[tex]2\cdot10^{-7}\ meter\ \rightarrow\ \ the\ actual\ size\\\\scale=4\cdot10^2\\\\the\ size\ under\ the \ microscope\ \\\\=4\cdot10^2\cdot2\cdot10^{-7}\ meter=8\cdot10^{-5}\ meter\\\\Ans.\ the\ size\ under\ the \ microscope\ is\ 8\cdot10^{-5}\ meter.[/tex]