Fixing the camera's left side in a 2D Game in all screen resolutions

I just started making a 2D game using unity and I have a resolution & cam problem. I have a 2D terrain and i'm trying to fix the left side of the cam to the left side of the terrain. However, when I change the screen resolution to iphone 4 for example, the left side is hidden. I tried this script for the cam but it's not working :

 void Awake()
 {        
     Ray ray = Camera.main.ScreenPointToRay(new Vector3(Screen.width/ 2, Screen.height / 2,-10));
     Camera.main.orthographicSize = ray.origin.y;
     transform.position = new Vector3 (ray.origin.x, ray.origin.y,-10);  
 }