如何为通用应用程序设置启动画面的大小和背景

I am using Default.png for iPhone and Default-Landscape.png for ipad. But in case of ipad the splash screen shows only half of the image and rest is cut. It seems to be the size of image becomes double of what it should be. I am using image with width:525 and height:175 for ipad.I am using Default.png for iPhone and Default-L