Electromagnetic Spectrum & Atmosphere question from JEE Main 2016 (9 Apr, Shift 1)

Answer: (c)

1. Microwave oven frequency ($\approx 2.45\ \text{GHz}$) lies in the range of rotational motion of polar water molecules.
2. The oscillating electric field makes the water dipoles rotate back and forth; this energy is shared as heat.
3. Vibrational energy levels of molecules correspond to infrared, not microwave, frequencies.
4. So, physically, the answer is (b) rotational energy to water molecules.