A sinusoidal electromagnetic wave emitted by a mobile phone has a wavelength of 34.8 cm and an electric-field amplitude of 5.70×10−2 V/m at a distance of 210 m from the phone. Calculate
(a) the frequency of the wave;
(b) the magnetic-field amplitude;
(c) the intensity of the wave.

a)

b)  

c)

Explanation:

a) The frequency (f) of the wave can be found as follows:

Where:

c: is the speed of light = 3x10⁸ m/s

λ: is the wavelength = 34.8 cm

b) The magnetic-flied amplitude (B) is:

Where:

E: is the electric field amplitude = 5.70x10⁻² V/m

c) The intensity of the wave (I) is the following:

Where:

μ₀: is the permeability of free space =  1.26x10⁻⁶ m*kg/(s²A²)  

I hope it helps you!

0.11 m/s and 0.28 m/s should be correct