how can a double stranded rna silence the mrna or be complimentary to it??? i think quite a few people seem to have this doubt.please help

double stranded rna cannot pass through the nuclear pore even if it reaches cytoplasm ribosome cannot bind to it  it can be translated only if itis single stranded...that meansit is silenced.and  actually the source  of the complementary rna  could be a viral infection or mobile genetic elements that replicate via an rna intermediate