[jQuery] looping through json

[jQuery] looping through json


how can i loop through json like:
{ "departments": {
"department": {"ID": 1, "Name": "Physics"},
"department": {"ID": 2, "Name": "Chemistry"},
"department": {"ID": 3, "Name": "Biology"}
}}
i tried
$.each(json.departments.department, function(i, n) {
    alert(i + " " + n);
});
and got
ID: 3
Name: Biology
but i wanted something like
1: Physics
2: Chemistry
3: Biology