Multiple Choice QuestionsAssertion: Television signals are received through sky-wave propagation.
Reason: The ionosphere reflects electromagnetic waves of frequencies greater than a certain critical frequency
If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion
If assertion is true but reason is false
If both assertion and reason are false
Assertion: Microwave communication is peferred over optical communication.
Reason: Microwaves provide large number of channels and bandwidth compared to optical signals.
if both assertion and reason are true but reason is the correct explanation of assertion
if both assertion and reason are true and the reason is not the correct explanation of assertion
if assertion is true and reason is false
if both assertion and reason are false statements
Assertion: In high latitudes one sees colourful curtains of light hanging down from high altitudes.
Reason: The high energy charged particles from the are deflected to polar regions by the magnetic field of the earth.
if both assertion and reason are true and the reason is the correct explanation of the assertion
if both assertion and reason are true and the reason is not the correct explanation of the assertion
if assertion is true but reason is false
if both assertion and reason are false statements
A.
if both assertion and reason are true and the reason is the correct explanation of the assertion
Earth is surrounded by its magnetic field in space called magnetosphere, which forms a barrier to Solar wind. The solar wind pressure strongly compresses the magnetosphere on the dayside and draws it out into an extremely long tail on the night side of the earth. Since, the charged particles of the solar wind cannot cross the earths magnetic field lines they flow around the magnetosphere. This forms a standing shock wave in space upstream of the earth. The magnetosphere and the solar wind form an enormous electrical dynamo where large and complicated electrical currents flow. These electrons descend down to altitudes of 100 - 300 km they may collide with the atmospheric gas causing it to glow. This is the basic cause of aurora.
Aurora is a natural electrical phenomenon characterized by the appearance of streamers of reddish or greenish in the sky, especially near the northern or southern magnetic pole.
Note that the plasma sheet is only connected to magnetic field lines from the earths Polar Regions on the night sight, which explains why the aurora is mostly seen only at high latitudes at night.
High-frequency waves are
affected by the solar cycle
reflected by layer
absorbed by the
capable of use for long-distance communication on the moon
The principle of LASER action involves
amplification of particular frequency emitted by the system
population inversion
stimulated emission
All of the above
Through which mode of propagation, the radio waves can be sent from one place to another?
Ground wave propagation
Sky wave propagation
Space wave propagation
All of the above
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