This question has Statement -1 and Statement -2 . Of the four choices given after the statements, choose the one that best describes the two statements.
Statement-1: Sky wave signals are used for long distance radio communication. These signals are in general, less stable than ground wave signals.
Statement-2 : The state of ionosphere varies from hour to hour, day to day and season to season.
Statement-1: Sky wave signals are used for long distance radio communication. These signals are in general, less stable than ground wave signals.
Statement-2 : The state of ionosphere varies from hour to hour, day to day and season to season.
- (A)Statement-1 is true, Statement-2 is true; Statement-2 is the correct explanation of Statement-1.✓ Correct
- (B)Statement-1 is true, Statement-2 is true; Statement-2 is not the correct explanation of Statement-1.
- (C)Statement-1 is false, Statement-2 is true.
- (D)Statement-1 is true, Statement-2 is false.
Answer: (A)
Solution
Both statements here are true, and the second genuinely accounts for the first. Sky waves are bent back to the ground by the ionosphere, which lets them cover long distances, but the ionosphere is not a fixed mirror: its degree of ionisation shifts from hour to hour, between day and night, and across the seasons. Because the reflecting layer keeps changing, the sky-wave signal fluctuates and is less steady than a ground wave that hugs the Earth's surface. The temporal variation of the ionosphere is therefore the very reason the sky-wave signal is the less stable of the two, so both statements are true and the second is the correct explanation of the first.
JEE Main · 2011 · 10 Apr 2011 · Offline · Single correct option