$(window).scroll(function() {

    var winHeight = $(this).height();

    var scrollTop = $(this).scrollTop();

    var elemHeight = $("#first-section").height();

    var elementTop = $("#first-section").position().top; 

    if (elementTop < scrollTop + winHeight && scrollTop < elementTop + elemHeight)

        $("your-div").addclass("active");

    else

        $("your-div").removeClass("active");

});