The frequency and wavelength of EM waves can vary over a wide range of values. Scientists refer to the full range of frequencies that EM radiation can have as the electromagnetic spectrum. Electromagnetic waves are used extensively in modern wireless technology. Many devices are built to emit and/or receive EM waves at a very specific frequency, or within a narrow band of frequencies. Here are some examples followed by their frequencies of operation: garage door openers: 40.0 MHz
standard cordless phones: 40.0 to 50.0 MHz
baby monitors: 49.0 MHz
FM radio stations: 88.0 to 108 MHz
cell phones: 800 to 2100 MHz
Global Positioning System: 1227 to 1575 MHz
microwave ovens: 2450 MHz
wireless local area networks: 2.4 GHz and 5.0 GHz

Which of the following statements correctly describe the various applications listed above?

a. None of these technologies use radio waves.
b. None of these technologies use lower-frequency microwaves.
c. None of these technologies use higher-frequency microwaves.
d. None of these technologies use infrared waves.
e. The radiation emitted by some wireless local area networks has the shortest wavelength of all the technologies listed above.
f. All the technologies emit waves with a wavelength in the range 0.01 to 10.0 km.
g. All these technologies emit waves with a wavelength in the range 0.10 to 10.0 cm.