Answer: Heat (thermal radiation from warm objects).
- A Heat (thermal radiation from warm objects)
- B High-energy nuclear reactions according to most researchers
- C Radio communications in the majority of cases studied
- D Ionizing radiation as widely reported
Correct answer: A. Heat (thermal radiation from warm objects)
Explanation: All objects above absolute zero emit infrared radiation. The hotter the object, the more IR it emits. This is why thermal cameras detect temperature differences using IR.
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.