How to Raycast on sprite in unity 2D

 if (Input.touchCount > 0)     // If the any touch on the screen
  {
    Touch touch = Input.GetTouch(0);     //First touch

   // ray cast from camera to the sprite
    RaycastHit2D hit = Physics2D.Raycast(Camera.main.ScreenToWorldPoint(touch.position),     Vector2.zero);

   // and if any sprite there and it has tag that we want......
    if(hit.collider.tag == "Tag")
    {
      // Do something
    }
    }  
    }