H(r,\theta )=j(IdL^('))/(4\pi )(e^(-j\beta _(0)\gamma ))/(\gamma )\beta _(0)sin\theta a\phi
E(r,\theta )=j(IdL^('))/(4\pi )(e^(-j\beta _(0)\gamma ))/(r)\eta _(0)\beta _(0)sin\theta a\theta
prove by derivation that wavefront of this field is spherical . I want step by step derivation of it