Suppose the name of div hidden is Q2, Please place this code in Q1's footer:
<script type="text/javascript">
function SSI_CustomGraphicalRadiobox(GraphicalRadioboxObj, InputObj)
{
var z=($("input[type=radio]:checked").val());
//alert(z);
if(z==1)
{
$("#Q2_div").show();
}
if(z>1)
{
$("#Q2_div").hide();
if($('#Q2').val() != "")
{
$('#Q2').val("");
}
}
}
</script>