Question

11. A radio station broadcasts their signal with a wavelength of 3.5 ?m. Although your radio will translate this signal into audible sound, explain why you cannot hear the radio signal directly.

Answer 1

If you could somehow make your eardrums sensitive to changes in the electromagnetic field, then yes, you could easily hear radio waves in the 20Hz - 20kHz range.

But your eardrums are not sensitive to changes in the electromagnetic field. So regardless of frequency, your ears are completely "blind" to radio waves.

What your eardrums do sense are changes in air pressure, to which they respond mechanically. These changes in air pressure are what we call sound. Although both sound and radio waves are characterized by frequency, beyond that they are very different in nature. Just think that whereas sound requires a medium in which it travels (air), electromagnetic waves propagate just fine in a vacuum. Sound travels at around 330 meters a second; electromagnetic waves, at around 300,000,000 meters per second, almost a million times faster. Nonetheless, as I said before, if somehow you could turn your eardrums into effectively an antenna, you could hear radio waves just fine. But your eardrums don't function as an antenna so you can't.