Here are 2 radio buttons namely rd1 and Radio1
<input type="radio" name="rd" id="rd1" />
<input type="radio" name="rd" id="Radio1" />
The simplest wayt to check which radio button is checked ,by checking individual is(":checked") property
if ($("#rd1").is(":checked")) {
alert("rd1 checked");
}
else {
alert("rd1 not checked");
}