Thinking Physics -Vibrations
Mixed up Before the advent of the radio and telephone, long distance messages were sent from one place to another by means of telegraph. A serious limitation of the telegraph was that only one message at a time could be successfully sent over a single telegraph wire.
Waves within waves The square wave and the sine wave shown in the sketch both have the same frequency and wavelength. Which of these waves contains the most high frequency or short wavelength component waves?
Quicksilver sea
地震波分为面波和体波，分别沿地球表面传播和在地球内部传播。而体波又分为P波（primary wave, or pressure wave）和S波（secondary wave, or shear wave）。前者是纵波，传播快，先被地震台接受到；后者是横波，传播慢，后被地震台接受到。爆炸和地震的最主要区别是，爆炸造成的震动模式主要是球对称，因此P波通常比S波强；而地震波主要来自地层缺陷的切向错位，因此S波通常更强。从各国地震台监测到的信号来看，P波强于S波，与自然地震信号有明显差异。 朝鲜2006年核试验信号（红色）的P波强于S波与附近地区的地震信号（蓝色）明显不同