Image confusion(electrostatics)

[Kolahal Bhattacharya]

Sir, when I was carrying out an image problem in electrostatics(a charge is kept near a grounded conducting sphere;we are to find the ratio of induced charges on the front face and on the rear one).The ratio comes positive.It seems to be correct as it matches with a teacher's comment.But I am thinking it should be negative.Because front face is induced with charge opposite to source charge,but the rear face is induced with the same type of charge as the source. Please help!

 

[andrevdh]

Why would there be any resultant charge on the rear of the sphere when it is grounded? What electrostatic force would hold this unbalanced charge there? If the sphere were not grounded one would naturally find the opposite charge on the rear of the sphere.