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General Studies I

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2008 Paper

Question
72 out of 150
 

Each of the following 3 questions consists of two statemetns, one labelled as ‘Assertion (A)’ and the other as ‘Reason (R)’. You are to examine these two statements carefully and select the answers to these items using the code given below.


Assertion (A): Radio waves bend in a magnetic field

Reason (R): Radio waves are electromagnetic in nature

Code:



A both A and R are individually true and R is the correct explanation of A
B Both A and R are individually true but R is not the correct explanation of A
C A is true but R is false
D A is false but R is true

Ans. A Electromagnetic (EM) radiation is a self-propagating wave in space or through matter. EM radiation has an electric and magnetic field component which oscillate in phase perpendicular to each other and to the direction of energy propagation. Electromagnetic radiation is classified into types according to the frequency of the wave, these types include (in order of increasing frequency): radio waves, microwaves, terahertz radiation, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays. Of these, radio waves have the longest wavelengths and Gamma rays have the shortest. A small window of frequencies, called visible spectrum or light, is sensed by the eye of various organisms, with variations of the limits of this narrow spectrum. Light is sometimes used in a broader sense, referring to EM radiation.

Radio waves also bend. Recall our discussion that water absorbs and affects radio waves? Variations in water vapor in the air can bend radio waves and plays an important part in a phenomenon called tropo duct openings.

Normally, air temperature continuously decreases as one goes higher in the atmosphere. Occasionally, a weather phenomenon called a temperature inversion occurs that traps a pocket of warm air at higher altitudes. The warm air is sandwiched between two layers of cooler air.

Since warm air can hold more moisture, it has more water vapor than the surrounding cooler, dry air. Radio signals travel slower in the warm, moist air than in the cooler air. This causes the cool air to bend or refract radio signals towards the warmer air. In effect, the two layers of cool air now form a wave guide

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