$\bullet$ Consider electromagnetic waves propagating in air. (a) Determine the frequency of a wave with a wavelength of (i) $5.0 \mathrm{km},$ (ii) $5.0 \mu \mathrm{m},$ (iii) 5.0 $\mathrm{nm}$ . (b) What is the wavelength (in meters and nanometers) of (i) gamma rays of frequency $6.50 \times 10^{21} \mathrm{Hz}$ , (ii) an AM station radio wave of frequency 590 $\mathrm{kHz} ?$