2. (1 pt.) Fill in the two blanks in the following explanation: Question: Back in PHYS 151, we mentioned that the range of human hearing is 20 Hz to 20 kHz. How is it that we are able to hear a radio station if it broadcasts frequencies like 1000 kHz (AM radio) or 100 MHz (FM radio)? Answer: A radio station combines its "program" or audio-frequency signal (audible frequencies between 20 Hz and 20 kHz) with its "carrier" frequency (the broadcast frequency assigned to the station, such as 90.3 MHz) using one of two methods: stations. The modulated radio signal is then broadcast and received by any nearby radio tuned to the carrier frequency modulation for "AM" stations, or modulation for "FM" Every radio contains a demodulator to separate the program signal from the carrier wave. Only the program signal is then sent to the radio's speakers. The speakers then vibrate at the audible frequencies of the program signal (between 20 Hz and 20 kHz) to recreate the audio program, but they never vibrate at 90.3 MHz that frequency was simply the "carrier wave" and is discarded by the radio. The loudspeakers vibrate, creating pressure waves at the same frequencies in the surrounding air, and the waves then travel to our ears where we hear them as sound. (Also, note that our ears can hear only sound waves; we cannot hear radio [electromagnetic] waves!)