It is because Barium and Strontium are both elements of same group and have same outer shell configuration of ns2
where n is the principal quantum number or shell number.
Furthermore, they both are bonded to same element.
Hence, the formula of Barium and Strontium Chloride are similar.
No, a beam of electrons is used by an electron scanning microscope. A light microscope uses light waves either reflected off the surface of the object under study, or passed through the object from beneath. Some people might consider a light wave as a type of electron beam, but for the purposes of microscopy, the ESM is capable of far greater magnification than the LM.