The app might be minimized in the Dock, or it might be somewhere on the desktop hiding behind other windows. If the green indicator light is still on, you haven't properly closed the app, and the iSight camera is still on. Look for the green indicator light to go off when closing the app to turn the iSight camera off.Minimize the app to access other programs while keeping the iSight camera ready. Select the yellow minimize button in the top left corner of an app to temporarily tuck it away without closing it or turning the camera off.