What mode of propagation is used for the Ultra high frequency range?

The correct answer is Option (3) → Space waves

The mode of propagation of a radio wave depends on its frequency. The ultra high frequency (UHF) range is about 300 MHz to 3 GHz, far above the few tens of MHz up to which the ionosphere can reflect waves back to the earth.

At UHF the wave goes straight through the ionosphere, so it travels in a straight line from the transmitting to the receiving antenna as a space wave (line-of-sight); television and mobile signals use this mode.

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):
Space Wave – “Another mode of radio wave propagation is by space waves. A space wave travels in a straight line from transmitting antenna to the receiving antenna. Space waves are used for line-of-sight (LOS) communication as well as satellite communication. At frequencies above 40 MHz, communication is essentially limited to line-of-sight paths.”