## Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (3rd Edition)

(a) $f = 1.5\times 10^{9}~Hz$ (b) $\lambda = 1.0\times 10^{-6}~m$
(a) We can find the frequency of an electromagnetic wave with a wavelength of 20 cm. $f = \frac{v}{\lambda}$ $f = \frac{3.0\times 10^8~m/s}{0.20~m}$ $f = 1.5\times 10^{9}~Hz$ (b) We can find the wavelength of a sound wave in water which has this frequency. $\lambda = \frac{v}{f}$ $\lambda = \frac{1500~m/s}{1.5\times 10^{9}~Hz}$ $\lambda = 1.0\times 10^{-6}~m$