Question

Why does radio reception improve slightly during the night ?

• A. The outside noise is reduced very much at night.
• B. Unlike the daytime, only a few radio stations broadcast during the night.
• C. Sunlight affects radio broadcasts to some extent during the day.
• D. The magnetic field of the earth acts with reduced intensity during the night, thereby reducing its impact on broadcasts.

Answer 1

Answer: (C)

Sunlight affects radio broadcasts to some extent during the day.

Answer is C.
The D region is the lowest of the regions within the ionosphere that affects radio communications signals to any degree. It is present at altitudes between about 60 and 90 kilometers and the radiation within it is only present during the day to an extent that affects radio waves noticeably. It is sustained by the radiation from the Sun and levels of ionization fall rapidly at dusk when the source of radiation is removed. It mainly has the affect of absorbing or attenuating radio communications signals particularly in the LF and MF portions of the radio spectrum, its affect reducing with frequency. At night it has little effect on most radio communications signals although there is still a sufficient level of ionization for it to refract VLF signals.
Hence, radio reception improve slightly during the night because, sunlight affects radio broadcasts to some extent during the day.