AIIMS 2006
- Exam
- AIIMS
- Year
- 2006
- Subject
- Physics
- Chapter
- Communication System
AIIMS 2006 · Physics · Communication System
Assertion : Electromagnetic waves with frequencies smaller than the...
Assertion : Electromagnetic waves with frequencies smaller than the critical frequency of ionosphere are used for communication using sky wave propagation.
Reason : The refractive index of the ionosphere becomes very high for frequencies higher than the critical frequency.
Options
- AIf both assertion and reason are true and reason is the correct explanation of the assertion
- BIf both assertion and reason are true but reason is not the correct explanation of the assertion
- CIf assertion is true, but reason is false
- DBoth assertion and reason are false statements.
Correct answer
B. If both assertion and reason are true but reason is not the correct explanation of the assertion
Step-by-step solution
If the frequencies of the waves are less than that of the critical frequency. They will be reflected back as the ionosphere has refractive index less than free space. This is the principle of sky wave propagation.
The statement given in the
Reason that the refractive index becomes high is correct. But the Reason given is not true for the assertion.