10.18 Two towers on top of two hills are 40 km apart. The line joining them passes 50 m above a hill halfway between the towers. What is the longest wavelength of radio waves, which can be sent between the towers without appreciable diffraction effects?

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Payal Gupta | Contributor-Level 10

9 months ago

10.18 Distance between the towers, d = 40 km

Height of the line joining the hills, h = 50 m

Thus, the radial spread of the radio wave should not exceed 40 km

Since the hill is located halfway between the towers,

Fresnel's distance $Z_{P}$ = $\frac{40}{2}$ = 20 km = 2 $* 10^{4} m$

Aperture can be taken as a = h = 50 m

Fresnel's distan

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