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Statement-I : Electromagnetic waves with...

Statement-I : Electromagnetic waves with frequencies smaller than the critical frequency of ionosphere cannot be used for communication using sky wave propagation
Statement-II : The refractive index of the ionosphere becomes very high for frequencies higher than the critical frequency.

A

Statetment-I is True, Statement-II is True , Statement-II is a correct explanation for Statement-I

B

Statement-I is True, Statement-II is True , Statement-II is NOT a correct explanation for Statement-I

C

Statement-I is True, Statement-II is False

D

Statement-I is False, Statement-II is True

Text Solution

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The correct Answer is:
D
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ALLEN -SEMICONDUCTORS-Part-3(Exercise-3)
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  2. Assertion: The Microwave propagation is better than the sky wave propa...

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  3. Statement-I : Semiconductors do not obey Ohm's law Statement-II : El...

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  4. Statement-I : Germanium is preferred over silicon for making semicondu...

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  5. Assertion : p-n junction diode can be used even at ultra high frequenc...

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  6. Statement-I : A p-n junction with reverse bias can be used as a photod...

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  7. Assertion: NAND or NOR gates are called digital building blocks. Rea...

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  8. Assertion: Two P-N junction diodes placed back to back, will work as a...

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  9. Statement-I : When base region has larger width, the collector current...

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  10. Statement-I : For faster action, n-p-n transistor is used Statement-...

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  11. Statement-I : To be used as amplifier, the transistor in the common em...

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  12. Statement-I : Many channels get allowed when transmission frequency is...

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  13. Statement-I : Optical fibres are free from electromagnetic disturbance...

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  14. Statement-I : Diode lasers are used as optical sources in optical comm...

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  15. Statement-I : Electromagnetic waves with frequencies smaller than the ...

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  16. Statement-I : In optical fibre, the diameter of the core is kept small...

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  17. Statement-I : For the same antenna length, power radiated by short wav...

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  18. Statemet-1: the electrical conductivity of earth's atmosphere increase...

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  19. Assertion:- Optical communication system is more economical than other...

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  20. Statement-I : A communication satellite is essentially a repeater in s...

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