Download App

Communication — JEE physics STD 12 Science — Question

CBSE BoardEnglish MediumSTD 12 ScienceJEE physicsCommunication1 Mark
Question
Assertion : Television signals are received through sky-wave propagation.
Reason : The ionosphere reflects electromagnetic waves of frequencies greater than a certain critical frequency.
✓

Answer

(d) TV signals (frequency greater than $30 \mathrm{MHz}$ ) cannot be propagated through sky wave propagation.Above critical frequency, an electromagnetic wave penetratates the ionosphere and is not reflected by it.

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

More "Assertion & Reason" from Communication→Communication — all question types→JEE physics STD 12 Science question papers→CBSE Board STD 12 Science question papers→CBSE Board question paper generator→

Similar questions

Assertion : The velocity of sound increases with increase in humidity.
Reason : Velocity of sound does not depend upon the medium.
→
Assertion : Glassy solids have sharp melting point.
Reason : The bonds between the atoms of glassy solids get broken at the same temperature.
→
Assertion : The isothermal curves intersect each other at a certain point.
Reason : The isothermal change takes place slowly, so the isothermal curves have very little slope.
→
Assertion : Friction is a self adjusting force.
Reason : Friction does not depend upon mass of the body.
→
Assertion : The temperature coefficient of resistance is positive for metals and negative for P-type semiconductor.
Reason : The effective charge carriers in metals are negatively charged whereas in $P$-type semiconductor they are positively charged.
→
Assertion : The polar caps of earth are cold in comparison to equatorial plane.
Reason : The radiation absorbed by polar caps is less than the radiation absorbed by equatorial plane.
→
Assertion : The position-time graph of a uniform motion in one dimension of a body can have negative slope.
Reason : When the speed of body decreases with time, the position-time graph of the moving body has negative slope.
→
Assertion : Diode lasers are used as optical sources in optical communication.
Reason : Diode lasers consume less energy.
→
Assertion : Speed of wave $=\frac{\text { Wave length }}{\text { Time period }}$
Reason : Wavelength is the distance between two nearest particles in phase.
→
Assertion : A spring has potential energy, both when it is compressed or stretched.
Reason : In compressing or stretching, work is done on the spring against the restoring force.
→