Answer: Radio waves.
- A X-rays
- B Ultraviolet
- C Radio waves
- D Gamma rays
Correct answer: C. Radio waves
Explanation: Radio waves have the lowest frequency and hence the longest wavelength in the electromagnetic spectrum; gamma rays have the shortest.
In an electromagnetic wave, the oscillating electric field (E) and magnetic field (B) are perpendicular to each other and to the direction the wave travels - a purely transverse wave that needs no medium, unlike sound.
Concept context
Maxwell's equations, EM spectrum, properties, and applications of each band.