I want to get the height of an object that the raycast hit. What I can do?
Considering you know how to use Raycast and what is GameObject:
RaycastHit hit;
if (Physics.Raycast(rayOrigin, rayDirection, out hit, maxDistance))
{
GameObject hitObject = hit.collider.gameObject;
//do whatever you want with your hit object, GetComponenets, position, size, etc.
}