frequency is equal to number of oscillations or vibrations upon time
therefore,
check picture
The frequency of the wave is 
Explanation:
The frequency, the wavelength and the speed of a wave are related by the following equation:

where
c is the speed of the wave
f is the frequency
is the wavelength
For the radio wave in this problem,


Therefore, the frequency is:

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Answer:
c = 1 / √(ε₀*μ₀)
Explanation:
The speed of the electromagnetic wave in free space is given in terms of the permeability and the permittivity of free space by
c = 1 / √(ε₀*μ₀)
where the permeability of free space (μ₀) is a physical constant used often in electromagnetism and ε₀ is the permittivity of free space (a physical constant).
This is possible due to self-discharge. Very small internal currents inevitably occur in these cells over time and they will eventually exhaust the chemistry.