Newall, H. F · London : Society for Promoting Christian Knowledge · leaf 26
at D D (or through any setof corresponding points either on the rising or on thefalling side of a wave, as at E E), also advance, andthe feature of the advance is that these lines travelparallel to one another, and at right angles to thedirection of propagation. In the figure, the inclina-tion of… … that the fronts are always at right angles to thedirection in which they travel. We see that eachline A A, D D, E E has been drawn through a set ofcontiguous points at which the phase of the wave-motion is similar, A A through points on one and thesame crest, D D along one and the same trough, and…
Spectroscope · Spectrum analysis
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