Raycast 2D

Hi, I want to make a thing that if it comes close to a collider it pushes back (This case up). But what do I need to change to get it to work for 2D?

 using UnityEngine;
 using System.Collections;
 
 public class Cast : MonoBehaviour {
     public Rigidbody2D RigidBody;
     public float Force = 100f;
     void Update () 
     {
         RaycastHit2D hit;
 
         Vector2 down = transform.TransformDirection (Vector2.down) * 10;
         Debug.DrawRay (transform.position,down,Color.green);
 
         if(Physics2D.Raycast(transform.position,(down), out hit))
         {
             if (hit.distance <= 5) 
             {
                 GetComponent<Rigidbody2D> ().AddForce (Vector2.up * Force);
                 print ("Hit");
             }
         }
     }
 }
 

Thanks for reading. -CoasterMind