How to use a function from another script

using UnityEngine;
using System.Collections;

public class Obstacle : MonoBehaviour {

	void OnCollisionEnter2D(Collider2D coll){

	}
}

How do I call a function from the “Death” Script if a obstacle using this script hits the player?
And please explain the steps if you can. Thank you.

using UnityEngine;
using System.Collections;

public class Death : MonoBehaviour {

	// Use this for initialization
	void Start () {
	
	}
	
	// Update is called once per frame
	void Update () {
	
	}

}

void OnCollisionEnter2D (Collider2D col)
{
if (col.GetComponent()) //If the object has the death script, execute the function
col.GetComponent().StartDeath (); //Call the ‘StartDeath’ function from the ‘Death’ script
}
And then in your ‘Death’ class, you would simply have something like the following;

void StartDeath ()
{
    //Do stuff
}