Diffraction is the ability of a wave to bend around an obstacle or the edges of an opening. Would you expect AM or FM radio waves to bend more readily around an obstacle such as a building?
The correct answer and explanation is:
Correct Answer: AM radio waves bend more readily around an obstacle such as a building.
Explanation:
Diffraction is a fundamental property of waves that refers to their ability to bend around obstacles or spread out after passing through narrow openings. The extent to which a wave diffracts depends on its wavelength. Longer wavelengths are more capable of bending around large objects compared to shorter wavelengths.
AM (Amplitude Modulation) radio waves typically have frequencies between 530 and 1700 kHz, which correspond to wavelengths ranging from about 180 to 570 meters. FM (Frequency Modulation) radio waves have frequencies between 88 and 108 MHz, corresponding to wavelengths between about 2.8 and 3.4 meters.
Because AM radio waves have much longer wavelengths than FM waves, they are better suited for diffraction. This makes them more capable of traveling around buildings, hills, and other obstacles. That is why AM radio can often be heard in places where FM signals cannot reach clearly, such as in tunnels, behind tall structures, or in rural valleys.
FM signals, having much shorter wavelengths, do not bend as easily around obstacles. They tend to travel in straighter lines and are more easily blocked by solid objects. This leads to more limited range and greater signal loss in urban or mountainous areas where buildings or terrain might obstruct the signal path.
In practical terms, this difference in diffraction is one reason why AM stations often provide more reliable long-distance coverage, especially at night when atmospheric conditions enhance their range. FM, while offering better sound quality, is more limited in reach due to its weaker diffraction abilities. Therefore, in situations where bending around obstacles is crucial, AM radio waves perform better.