light intensity change with easing problem!!

hi i have this script named light control.js

 var sun : GameObject;
 var lightchange: float = 0.1;
 var lightnormal: float = 0.7;
  
  
 function OnTriggerEnter() {
     sun.light.intensity = lightchange;
     
 }
  
 function OnTriggerExit() {
     sun.light.intensity = lightnormal;
 }

now as you can see i have a collider trigger to decrease the intensity of sun(directional light). but the problem is the intensity changed quickly without any easing effect...

i searched a lot to how to easing the changing between them but cant actually add them to my script to make it working... :( Tell me how to do the easing thing and how to add that...