Resposive image with css

responsive-imgs.css

@media (min-width: 1000px) and (max-width:1380px){
    .politician-profile .bg-img{
        background-image: url(../img/fundo_app_dog_media.png);
        height: 90%;
    }
}

@media (min-width:720px) and (max-width:1000px){
    .politician-profile .bg-img{
        background-image: url(../img/fundo_app_dog_peq.png);
        height: 90%;
    }
}

@media (min-width:480px) and (max-width:720px){
    .politician-profile .bg-img{
        background-image: url(../img/fundo_app_dog_xpeq.png);
        height: 90%;
    }
}