jquery how to get the values of a radio button

Dear Experts,

In the following suitation how do I get the selected value (apple) of the radio button using jquery?

I tried:

alert( $("answer") );
alert( $("answer").value );
alert( $("answer").text );

I am new to jquery and didnt find it in the API :(

<form>
<input name="answer" type="radio" value="cake">answer 1<br />
<input name="answer" type="radio" value="apple" checked>answer 2<br />
<input name="answer" type="radio" value="waterlemon">answer 3<br />
</form>

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