Raycast line display shooting

How to display a raycast line?

#pragma strict
var Effect : Transform;
var TheDammage = 30;

function Update () {
	
	var hit : RaycastHit;
	var ray : Ray = Camera.main.ScreenPointToRay(Vector3(Screen.width*0.5, Screen.height*0.3, 0));
	
	if (Input.GetMouseButtonDown(0))
	{
		if (Physics.Raycast (ray, hit, 100))
		{
			var particleClone = Instantiate(Effect, hit.point, Quaternion.LookRotation(hit.normal));
			Destroy(particleClone.gameObject, 2);
			hit.transform.SendMessage("ApplyDammage", TheDammage, SendMessageOptions.DontRequireReceiver);
		}
	}
	
}

Hey I hope this link will help :