Two towers on the top of two hills are 40 km apart. The line joining them presses 50 m above a hill half way between the towers. What is the longest wavelength of radiowaves which can be send between the towers without appreciable diffraction effects?

Explanation

To solve the problem, we need to determine the longest wavelength of radio waves that can be sent between two towers without experiencing appreciable diffraction effects. We can use the formula related to diffraction:

\[ Z_f = \frac{a^2}{\lambda} \]

Where:
- \(Z_f\) is the distance from the line joining the tops of the towers to the hill (in this case, the height above the hill),
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