Making my ajax updated div fade in

I have this code that performs an ajax call and loads the results into two duplicate divs every time a dropdown is changed. I want the results to be faded into the div, to give a more obvious indication that something has changed, as its so seamless its sometimes hard to notice the change!

print("$('.ajaxdropdown').change(function(){


        $.ajax({
            type: "GET",
            url: "/includes/html/gsm-tariff.php",
            data: "c_name="+escape($(this).val()),
            success: function(html){
                $("#charges-gsm").html(html);
                                    //i want to fade result into these 2 divs...
                $("#charges-gsm-faq").html(html);
                $("#charges-gsm-prices").html(html);
            }
        });
    });");

I've tried appending the fadein method and a few other things, but no joy.