Various optical systems or geometries can be used to perform light measurements. For instance, the total power [flux] of a light source can be measured in all directions, in a specific direction or ...

KNAUER and Stern (Zs. f. Phys., 39, 775) have recently investigated the relation between the intensity of a beam of mercury molecules and the pressure in the oven or source chamber. They have found ...

Photoelectric sensors with background suppression are a more evolved version of the basic diffuse sensors used on public washroom sinks to control automatic faucets. Both in this rudimentary ...