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Two towers on top of two hills are 40 km...

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?

Text Solution

Verified by Experts

Size of aperature, `a= 50 m`
Distance of aperture from tower,
`Z_(F)= (40)/(2)km = 20xx 10^(3)m`
Fresnel distance, `Z_(F)= (a^2)/(lambda)" or "lambda= (a^2)/(Z_F)= (50xx 50)/(20xx 10^(3))m`
`=125xx 10^(-3)m = 12.5 cm`.
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