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130. Problem 19.38 (RHK) This problem uses the result of the problem 129 (19.38
RHK). Let us suppose that d = 230 km and H = 510 km. The waves
are 13.0 MHz radio waves ( |
).
At the detector D the combined signal strength varies from a maximum to zero
and back to a maximum again six times in 1 min. We have to find the speed
with which the reflecting layer is moving. We can assume that the layer is
moving slowly, so that the vertical distance moved in 1 min is small
compared to H and d.|
Solution: Click For PDF Version Data of the problem are
and v the speed of the wave is
In the problem it is given that the reflecting layer is moving with speed such that the signal strength at the detector varies from maximum to zero and back to maximum again six times in a minute. Let h be the distance moved by the reflecting layer in 1 min. This implies that
We have been given that the vertical distance h is small compared to H and d. In this approximation we use the result that
In this approximation, we have the result
Substituting the data of the problem, we find
Thus we find that the reflecting layer is moving with a speed of
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.
Therefore, the wavelength
of the
wave is
.