Lithium has a work function of 2.3ev. If 400nm light is incident on it, what is the maximum kinetic energy ? Chemistry Bohr Model of the Atom Calculations with wavelength and frequency
No. A comma precedes such as when what follows is an example of whatever went before. In this case, it is nonrestrictive. (For nonrestrictive constructions: use a comma.).
No it's not always necessary to add a comma before instead. Ill give you some counterexamples in the following sentences where there's no comma needed before instead. I was going to go shopping, but I went dancing instead.