World Bounds From Config

var config = {
    type: Phaser.WEBGL,
    width: 800,
    height: 600,
    parent: 'phaser-example',
    physics: {
        default: 'impact',
        impact: {
            gravity: 100,
            setBounds: true,
            maxVelocity: 500
        }
    },
    scene: {
        preload: preload,
        create: create
    }
};

var game = new Phaser.Game(config);

function preload ()
{
    this.load.image('gem', 'assets/sprites/gem.png');
}

function create ()
{
    //  The world bounds have been set in the config.
    //  setBounds: true is the same as calling physics.world.setBounds() with no arguments

    //  If you don't set the body as active it won't collide with the world bounds
    this.impact.add.image(300, 300, 'gem').setActiveCollision().setVelocity(300, 200).setBounce(1);
}