Final answer:
The minimal frequency that an electromagnetic wave should have to resolve an object of size 20m is 20,000 Hz.
Step-by-step explanation:
The minimal frequency of an electromagnetic wave required to resolve an object with a size of 20m relates to the concept of wave diffraction and resolution. To resolve such a size, the wavelength should be smaller or comparable to the size of the object. Given that the speed of an electromagnetic wave (which is the speed of light for electromagnetic waves in vacuum) is significantly higher than the example speed provided, the frequency to resolve a 20m object would need to be higher than the example maximum frequency of 20,000 Hz.
To resolve an object of size 20m, the minimal frequency of the electromagnetic wave should be determined based on the formula: λ(min) = c / f(max) where λ(min) is the minimum wavelength, c is the speed of light, and f(max) is the maximum frequency. Given that the speed of light is 348.7 m/s and the maximum frequency is 20,000 Hz, we can substitute these values to solve for λ(min) as follows:
λ(min) = 348.7 m/s / 20,000 Hz = 0.017 m or 1.7 cm