getImageUrl() no returning any value in an external php

I am trying to display the image url in an external file. What I did is the following.

require_once '/var/www/html/app/Mage.php';
 Mage::app();
 $product = Mage:: getModel('catalog/product')->load(11);
 echo $product->getImageUrl();
 

But the $product->getImageUrl() didnot return any value.
The file is located in the root folder where the index.php is present.
When I print the $product->getImage() , it displayed the image name.

Is the getImageUrl() not a default function in magento ?

when i used the function $Image = $product->getMediaConfig()->getMediaUrl($product->getData('image'));
the image url is displayed.

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