Help me bounce (make player bounce when landing from a jump)

My player is a ball, and He jumps lovely, however upon landing I'd like him to jump again as you were, but with only half the force to simulate a bounce effect. Perhaps this would repeat again with 1/4 of the original force on the 3rd bounce. But I won't get to far ahead of myself.

The player's jump works as you'd imagine

PlayerScript:

 function Update () {
     
         var hit : RaycastHit;
             if (Physics.Raycast (transform.position, -Vector3.up, hit, 1.5)) {
                if (isFalling==false && Input.GetButtonDown("Jump")){ // only jump from the ground
             rigidbody.velocity.y += jumpSpeed;
         }
     }
 }

 function Jump (){
         if (Input.GetButtonDown("Jump") && isFalling==false){ // only jump from the ground
 
         rigidbody.velocity.y += jumpSpeed;
         }
         }

I don't really know how i'd even start this, so any pushes in the right direction are welcomed - with open arms.