Face detection code in Open CV

In my program i am detecting the face of a person, my code is working well, but i am worry about this code, as for eye detection "cascade.detectMultiScale()" have many parameters, while  for Face detection i am using these few parameters, and how it detects the face, whether we have not initialized the size of detecting object in  "cascade.detectMultiScale()"

     cascade.detectMultiScale(gray, faces, 1.2, 2);

    for (int i = 0; i < faces.size(); i++)
    {
        Rect r = faces[i];
        rectangle(src, Point(r.x, r.y), Point(r.x + r.width, r.y + r.height), CV_RGB(0,0,255));
    }