Oscillator phase transmission. Wavelength

Why, when you throw a stone into the water is calm, we again saw ripples spreading out from where the stone hit the water?


Take a thin elastic metal rods, mounted at the top of a small marble (or a needle). Place the metal rod so that marbles touch point P on the surface of a fairly large water tray. If elastic metal bar, just strummed lightly on top of the bar also makes marbles oscillation cycle period T, and the element of water in contact with it also oscillate with a period of T in a long time. On the waterfront of circular waves centered at P also spread out every way.


Suppose at time t = 0, the wave-shaped as in Figure a, the image below.

We see that the points A, E, I, on the water is fluctuating in phase with each other: they go through the equilibrium position and moving back down. The point C, G is the opposite phase oscillations with A, E, I: we go through the balance point and move upwards. Subscribe in the figure, we see that at time t = T / 4 (Figure b), the A-phase oscillations in t = 0 was transferred to B, and at the time t = T / 2 (Figure c), t = 3T / 4 (Figure d), t = T (Figure e) it in turn transmitted to the C, D, E. Phase oscillation transmitted horizontally, while the only element oscillating water vertical.

On the drawing we see two points E and I oscillate in phase with A. The distance between two points on the nearest transmission and in phase with each oscillation wavelength λ called. Generally, the points are separated by a whole number of wavelengths on the transmission, the oscillations in phase with each other. Three points I, E, A reverse-phase oscillations with G. The distance between I and G by half a wavelength. Generally, the points are separated by a half-wave odd number on the reverse-phase oscillations transmit different competition.

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