Question

Which statement about microwaves is correct?
A. Microwaves are longitudinal waves
B. The frequencies of microwaves are greater than the frequencies of visible light
C. The speed of microwaves in a vacuum is equal to the speed of visible light in a vacuum
D. The wavelengths of microwaves are smaller than the wavelengths of infra-red

Answer 1

Hint:Microwave is a kind of electromagnetic radiation with wavelengths ranging from roughly one metre to one millimetre and frequencies ranging from 300 MHz to 300 GHz. Microwaves are defined differently by different sources; the wide definition above encompasses both UHF and EHF (millimetre wave) bands.

Complete step by step answer:
Microwaves move in a straight line, unlike lower-frequency radio waves, and do not diffract over hills, follow the earth's surface as ground waves, or reflect off the ionosphere. As a result, terrestrial microwave communication lines are restricted to roughly 40 miles by the visible horizon (64 km). They are absorbed by gases in the atmosphere at the upper end of the spectrum, limiting practical communication range to approximately a kilometre.

Microwaves move in a straight line, unlike lower frequency radio waves, they do not travel as ground waves that follow the curvature of the Earth or reflect off the ionosphere (skywaves).Although they can penetrate through building walls enough for practical reception at the low end of the band, rights of way cleared to the first Fresnel zone are typically necessary.

As a result, microwave communication lines on Earth's surface are restricted to roughly 30–40 miles (48–64 kilometres) by the visible horizon. In vacuum, the speed of all types of electromagnetic radiation is equal to the speed of light. Microwaves have a longer wavelength than visible light, thus their frequency must be lower to maintain the same speed.

Hence option C is correct.

Note: For point-to-point telecommunications, microwave technology is widely utilised (i.e. non-broadcast uses). Microwaves are particularly well suited for this application because they can be focused into narrower beams than radio waves, allowing frequency reuse; their higher frequencies enable broad bandwidth and high data transmission rates; and antenna sizes are smaller than at lower frequencies because antenna size is inversely proportional to transmitted frequency.