Substitute Eqs. (7- 55) and (7-57) in Maxwell's equations to obtain wave equations for...

Substitute Eqs. (7- 55) and (7-57) in Maxwell's equations to obtain wave equations for scalar potential V and vector potential A for a linear, isotropic but inhomogeneous medium. Show that these wave equations reduce to Eqs. (7 - 65) and (7- 63) for simple media. (Hint: Use the following gauge condition for potentials in an inhomogeneous medium:.