code to set a select box option value as an object

You will not be able to store objects/arrays in the value attribute, however an option would be to use data-* attributes which supports json automatically with jQuery 1.4.3+

<select>
    <option data-value="{"name":"rajiv","age":"40"}">a</option>
    <option data-value="{"name":"mithun","age":"22"}">f</option>
</select>

And using .change()

$("select").change(function(){
    alert($(this).find(":selected").data("value").age);
});

Example on jsfiddle