Mountain Sickness

JOHN KNOTT
1917 Nature  
NATl!RE [MARCH 22, 1917 The fringes appear to be due to the intederence between two portions of light arising out of the single beam incident on the grating, one of them being reflected at the silvered surface and then diffracted out by the grating element which it meets, and the other being diffracted into the air space by the same grating element and then l·eflected out by the silvered surface. The path difference is equal to 21 (cos X -cos cf»
doi:10.1038/099064a0 fatcat:le4n56df7fgudhbbtklwsrif4m