property>energy per unit area
What is Energy per Unit Area?
Energy per unit area is a measure of the energy either impinging upon or generated from a given unit of area.
This can be a measure of the "toughness" of a material, being the amount of energy that needs to be applied per unit area of a crack to cause it to fracture. This is a constant for a given material. A tough material absorbs energy in deformation, while a brittle material such as glass does not have this ability and fractures easily once a crack is started.
The langley (abbreviation Ly) is used to quantify solar radiation and is named after 19th century American astronomer Samuel Langley.