Puate II. 
Decrease of intensity of penetrating radiation with height above the Earth’s surface. Intensity at surface is taken as unity. 
material in layers of different thicknesses. 
h 
Curve I. -11 em. 
Il. 1-1 em. 
III. 11:0 em. 
IV. = 
The various curves refer to intensities due to radioactive 
