Given below are two statements:
Statement (I): In a ground wave communication system, low frequency signal (\( \lt 2\,\mathrm{MHz} \)) can be transmitted.
Statement (II): If frequency is high then it will induce electrical signal on the surface of the earth and so attenuation takes place.
In the light of the above statements, choose the most appropriate answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Both Statement I and Statement II are correct
In ground wave (surface wave) propagation the wave glides along the surface of the earth. As it travels, it induces currents in the ground, and the energy absorbed by the earth weakens (attenuates) the wave. This loss grows rapidly with frequency.
Statement (I) — Correct. Because the attenuation rises with frequency, ground waves are useful only for low frequencies, up to about 2 MHz (medium-wave AM broadcasting is an example).
Statement (II) — Correct. The wave induces electric currents in the earth's surface and loses energy to it, and at high frequencies this attenuation becomes very large. That is why high-frequency signals cannot travel far as ground waves.
Note: This question is from the pre-rationalised NCERT book (2022-23). The topic was removed from the latest NCERT book (2026-27), and it also appears to be out of the CUET 2026 syllabus.
NCERT (Pre-rationalised edition, 2022-23):
Ground Wave – “… A wave induces current in the ground over which it passes and it is attenuated as a result of absorption of energy by the earth. The attenuation of surface waves increases very rapidly with increase in frequency. The maximum range of coverage depends on the transmitted power and frequency (less than a few MHz).”