Limiting camera to visible scene

I have a 2D map consisting of sprite GameObjects.

I have set up my camera so I can move it w arrows but i'm not sure how I should limit the camera to the borders of visible scene(so the user only sees actual tiles)

What I wanted is that the camera stops at the scene edges, but I'm not sure how to do this. Since I wrote a script that generates the 'game map' based on a number for columns/rows, I would like to have dynamic borders based on the scene's dimensions

this is my code so far:

using UnityEngine; using System.Collections;

public class CameraControl : MonoBehaviour {

 public float speed = 1.5f;


 // Use this for initialization
 void Start () {

 }
 
 // Update is called once per frame
 void Update () {


     if(Input.GetKey(KeyCode.RightArrow))
     {
             transform.Translate(new Vector2(speed * Time.deltaTime,0.0f));
     }
     if(Input.GetKey(KeyCode.LeftArrow))
     {
             transform.Translate (new Vector2 (-speed * Time.deltaTime, 0.0f));
     }
     if(Input.GetKey(KeyCode.DownArrow))
     {
             transform.Translate (new Vector2 (0.0f, -speed * Time.deltaTime));
     }
     if(Input.GetKey(KeyCode.UpArrow))
     {
             transform.Translate (new Vector2 (0.0f, speed * Time.deltaTime));
     }



 }

}