An observer is on top of a lighthouse whichis 25 metres high. The radius of the earth is 6367 kilometres. Howfar from the foot of the lighthouse, measured on the surface ofthe earth, is the horizon that the observer can see? < par/ > It is 32 kilometres (21 miles) across the Channel between Englandand France and you can see France from the cliffs of Dover. Howhigh must the cliffs be for it to be possible to see thatdistance?