Page:Ueber das Doppler'sche Princip.djvu/8

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If we substitute according to (10), it is, if $\textstyle{\sqrt{1-\frac{\varkappa^{2}}{\omega^{2}}}=q}$ is set:

$(W)=Ae^{\frac{2\pi(\mu y+\nu z)q}{T\omega}}\sin\frac{2\pi}{T}\left[t\left(1+\frac{\varkappa\sigma}{\omega}\right)-x\left(\frac{\sigma}{\omega}+\frac{\varkappa}{\omega^{2}}\right)\right].$

This gives for x = ϰt, if we write $\frac{\mu}{q}=\mu'$, $\frac{\nu}{q}=\nu'$:

$(\overline{W})=Ae^{\frac{2\pi(\mu'y+\nu'z)}{\omega T'}}\sin\frac{2\pi t}{T}\text{, where }T'=\frac{T}{1-\frac{\varkappa^{2}}{\omega^{2}}},$

thus we have an oscillating and at the same time propagating plane; however, the propagated displacement reads:

$(W)=Ae^{\frac{2\pi(\mu'y+\nu'z)}{\omega T'}}\sin\frac{2\pi t}{T}\left(t\frac{1+\frac{\varkappa\sigma}{\omega}}{1-\frac{\varkappa^{2}}{\omega^{2}}}-x\frac{\frac{\sigma}{\omega}+\frac{\varkappa}{\omega^{2}}}{1-\frac{\varkappa^{2}}{\omega^{2}}}\right){,}$

15)

where we now have $\sigma=\sqrt{1+(\mu^{'2}+\nu^{'2})q^{2}}$.

We notice that different laws as the Doppler principle are given, even if we limit ourselves to the first approximation, and ϰ²ω² is neglected compared to 1.

3) If the illuminating surface is a very small sphere of radius R, which oscillates according to the law for the rotation angle

$\overline{\psi}=A\sin\frac{2\pi t}{T}$

around the X-axis, then, at the distance $r=\sqrt{x^{2}+y^{2}+z^{2}}$ from the center of the sphere, the propagated rotations ψ are given by

$\psi=\frac{R^{3}A}{r^{3}}\left[\sin\frac{2\pi}{T}\left(t-\frac{r-R}{\omega}\right)+\frac{2\pi(r-R)}{T\omega}\cos\frac{2\pi}{T}\left(t-\frac{r-R}{\omega}\right)\right]$ $=\frac{R^{3}A}{r^{3}}\sqrt{1+\left(\frac{2\pi(r-R)}{T\omega}\right)^{2}}\cos\frac{2\pi}{T}\left(t-\frac{r-R}{\omega}-\eta\right){,}$

16)

where

$\frac{2\pi(r-R)}{T\omega}=\operatorname{ctg}\frac{2\pi\eta}{T}$