我如何使用文件夹名称中的随机名称访问图像？

I have a folder with one file and i need access to it using only the Folder name. This is basically the struct:

• Folder
  • File.ext (Random name)

For example: When i go to "http://example.com/Folder/" i need to redirect me to "http://example.com/Folder/File.ext".

I tried with ".htaccess" but not achieved what I need:

 RewriteEngine On
 RewriteBase /
 RewriteRule ^/Folder/$ /Folder/*.ext

Exists some regular expression to solve this problem with htaccess? or some other solution to this problem?

Aclaration: the folder only contains one file, and this file have a random name.