Chapter 32, Problem 32.55PP

BIO SAFE EXPOSURE TO ELECTROMAGNETIC WAVES.

There have been many studies of the effects on humans of electromagnetic waves of various frequencies. Using these studies, the International Commission on Non-Ionizing Radiation Protection (ICNIRP) produced guidelines for limiting exposure to electromagnetic fields, with the goal of protecting against known adverse health effects. At frequencies of 1 Hz to 25 Hz, the maximum exposure level of electric-field amplitude E_max for the general public is 14 kV/m. (Different guidelines were created for people who have occupational exposure to radiation.) At frequencies of 25 Hz to 3 kHz, the corresponding E_max is 350/f v/m, where f is the frequency in kHz. (Source: “ICNIRP Statement on the ‘Guidelines for Limiting Exposure to Time-Varying Electric. Magnetic, and Electromagnetic Fields (up to 300 GHz)’,” 2009; Health Physics 97(3): 257–258.)

32.55    Doubling the frequency of a wave in the range of 25 Hz to 3 kHz represents what change in the maximum allowed electromagnetic-wave intensity? (a) A factor of 2; (b) a factor of $1/\sqrt{2}$; (c) a factor of $\frac{1}{2}$; (d) a factor of $\frac{1}{4}$.