Electromagnetic waves are used extensively in modern 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 900 MHz, Global Positioning System: 1227 to 1575 MHz, microwave ovens: 2450 MHz, wireless Internet technology: 2.4 to 2.6 GHz.
Which of the following statements correctly describe the various applications listed above? Check all that apply.

a) All these technologies use radio waves.
b) All these technologies use have the same wavelength.
c) All these technologies use a combination of infrared waves and high-frequency microwaves.
d) Microwave ovens emit in the same frequency band as some wireless Internet devices.
e) The radiation emitted by wireless Internet devices has the shortest wavelength of all the technologies listed above.
f) All these technologies emit waves with a wavelength in the range of 0.10 to 10.0 km.