Practice portal › Electromagnetic Waves › Uses of the Bands, and lambda nu = c
Asked in GSEB Board July 2015 · Wavelength, frequency and photon energy
Given: u = 6×10⁹ Hz, and in air the speed is practically c = 3×10⁸ m s⁻¹.
Idea: the wave number here means the number of complete waves in a length of 1 m, which is 1/λ; and λ = c/ u, so the answer is just u/c.
λ = (3×10⁸)/(6×10⁹) = 0.05 m.
Number of waves in 1 m: 1/(0.05) = 20.
So the wave number is 20 per metre.
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