I posted this to some forum and got response , can somebody explain.
I think that when a charge system is put in a medium then the medium gets induced and exert force on the particle (test charge) thus net force is vector sum of forces by both medium and charge. this way force in particle due to charge should remain unaffected. correct me if I am wrong
￼ Answer was
The actual interaction between two charged particles through the exchange of photons which is a carrier of electromagnetic force. Your view is very very classical.