Texts: Stefan-Boltzmann Constant, σ = 5.67 x 10^-8 W/m^2 K^4. Speed of light is 3 x 10^8 m/s. III. a) A cordless telephone operates at a frequency of 8.5 x 10^8 Hz. What is the wavelength of these telephone waves? At what temperature does the maximum radiation occur?