In order to measure the length of a long flourescent ceiling lamp, a student makes a very small hole in a piece of paper, holds the paper above the floor, measures the distance between the hole and the floor, and finally measures the length of the light's image on the floor.
When the distance between the hole and floor is h 1 =20 cm , the image's length is l 1 =20 cm ; when the distance between the hole and floor is h 2 =33.333 cm , the image's length is l 2 =36 cm . What is the length L of the ceiling lamp in meters?