The needle of the speed-indicator flicked and wagged to and fro; the cinders rattled on the roof, and a whirl of dust sucked after the whirling wheels, The crew of the combination sat on their bunks, panting in their shirt- sleeves, and Cheyne found himself among them shouting old, old stories of the railroad that every trainman knows, above the ...
One of the main drawbacks to a digital TV signal or digital cable signal, for instance, is that it is an artificial reproduction of the original data, whereas an analog signal starts out as an exact copy of the original.
In this picture, an electromagnetic eigenmode of the periodic structure (called Bloch wave) is represented as a superposition of two counter-propagating waves that would exist in the absence of grating. Since neither of the components can propagate unaltered through the grating, they appear to interact between themselves.