Final answer:
The key difference between a radio wave and a sound wave is that radio waves are electromagnetic and can travel without a medium, whereas sound waves require a medium to propagate. AM radio waves, with lower frequency, have longer wavelengths compared to FM radio waves, which have higher frequency. Therefore, the correct option is 5) medium or no medium.
Step-by-step explanation:
A main difference between a radio wave and a sound wave is the medium or no medium required for their propagation. Sound waves are mechanical waves that create pressure variations in matter, such as air, water, or various solids.
In contrast, radio waves, which are a type of electromagnetic wave, do not require a medium and can travel through a vacuum, such as outer space. Radio waves, just like sound waves, have characteristics such as wavelength, frequency, and amplitude, but their nature of propagation is fundamentally different.
When comparing AM radio waves with FM radio waves, the former, which operates in the kilohertz range, has a longer wavelength compared to FM radio waves, which operate in the megahertz range.
This is because frequency and wavelength have an inverse relationship, as described by the formula c = λν, where c is the speed of light, λ (lambda) is the wavelength, and ν (nu) is the frequency. Therefore, lower frequency (such as AM radio) corresponds to a longer wavelength compared to higher frequency (FM radio) waves.