using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour {
      public float duration = 1.0F;
      void Update() {
          float phi = Time.time / duration * 2 * Mathf.PI;
          float amplitude = Mathf.Cos(phi) * 0.5F + 0.5F;
          light.intensity = amplitude;
      }
}