Conversion of wave quantities

(a)

Many cordless phones transmit and receive 900 MHz microwaves. Find the wavelength $\lambda$, the wavenumber $\kappa$, and propagation number $k$. Microwaves travel through air at speed $c=3.0\times 10^8$ m/s.

(b)

Microwave ovens generally operate at a frequency of $f=2.5$ GHz. Compute the wavelength of the waves inside an oven. In a brief sentence or two, use your answer to explain the hot and cold spots on a reheated pizza in a cheap microwave oven without a rotating dish.

(c)

Do problem YF 19-2 (p. 615).
Note: The normal range of human hearing is 20 Hz - 20,000 Hz.