why only one filename is written in using ls > in shell script : I'm stacked in coding shell script in my RedHatOS.

I tried to output filename using Regular expression as below。

    #!/bin/bash
    
    ls -1r rrr* > /tmp/memo.txt

and the result is this

/tmp/memo.txt

    /tmp/rrr1.txt

I want to descript all files on txt file like I did same thing in console

    $ls -1r rrr* > /tmp/memo.txt
    
    $cat /tmp/memo.txt

and the result of cat command is this

    /tmp/rrr1.txt
    /tmp/rrr2.txt

I don't understand what is happening,so please tell me why this occur and how to write all result of ls command. 

thanks.