Final answer:
Buildings don't block radio waves as completely as visible light because radio waves have longer wavelengths. X-rays have higher penetrating energy than visible light due to higher frequencies and shorter wavelengths. Radio waves are lower in frequency on the electromagnetic spectrum compared to visible light.
Step-by-step explanation:
The reason buildings don't block radio waves as completely as they block visible light is that radio waves have longer wavelengths than visible light, which allows them to diffract around obstacles better and penetrate different materials more easily. The correct answer to the question is (a) Radio waves have longer wavelengths than visible light.
Comparison of EM Radiation
X-rays carry more energy than visible light because they have shorter wavelengths (1 × 10⁻⁸ - 5 × 10⁻¹² m) and higher frequencies (3 × 10¹⁶ - 6 × 10¹⁹ Hz) compared to visible light, which has wavelengths of 7.5 × 10⁻⁷ - 4.0 × 10⁻⁷ m and frequencies of 4.0 × 10¹⁴⁵ x 10¹⁴ Hz. This indicates that visible light has lower frequencies and longer wavelengths than X-rays. Additionally, gamma rays have greater energy than visible light for penetrating matter due to even higher frequencies and shorter wavelengths.
On the electromagnetic spectrum, radio waves fall on the low-frequency side of visible light. When it comes to imaging techniques like observing broken bones, X-rays are used because they have high penetrating energy due to their high frequencies and short wavelengths compared to radio waves.