Once the light has been focused it can be magnified by different amounts using different eyepieces. This is why objects seem "closer" through a telescope.
The French inventor Augustin Fresnel had correctly deduced that light was pure energy that traveled in waves, and he then spent his life developing lenses and reflectors that could capture and concentrate light. The first lighthouse optics that he designed combined highly polished prisms with an array of lenses that captured light and concentrated it back into a main beam. The design was concentric in arrangement, funneling the light into a beam that was many times brighter than its source. This light could be seen for more than 20 miles.