Hi Lavanya,
The object which is genralized by Image/FileDoucment entity will have a attribute ‘Name’ which stores the File name. The file name is included with the Extension.
The other way to find extension is , you can make use of SubString function to fetch the file extension.
Example : $fileName= xxxxxxx_123.jpg
Use substring( $fileName,(FindLast($fileName,’.’)+1) this function will give you the extension.
or you can split the function as you want ,
Hope this helps!!!!