Propagation of Electromagnetic Waves in Atmosphere

Which mode of propagation is used by short wave broadcast services having frequency range from a few MHz upto 30 MHz?

In which of the following frequency ranges, use is made of ionosphere to reflect the electromagnetic waves for communication?

The typical frequency below which the ionosphere reflects the wave back to earth lies in the range

Line of sight propagation is

Which of the following modes is used for line of sight communication as well as satellite communication?

What should be height of transmitting antenna if the T.V. telecast is to cover a radius of $128 \mathrm{km}$ ?

(Radius of Earth $=6400 \mathrm{km}$)

By what factor the height of a transmitting antenna have to be changed so that the area covered by the telecast is doubled?

Usually microwave signals are not used for ionospheric propagation.The reason is

Identify the INCORRECT reasoning about why an audio signal of $10 \mathrm{kHz}$ frequency cannot be transmitted over long distances without modulation.

Sky wave propagation works due to the reflection of radio waves by the ________________________?

The navigation satellites provide _____ coordinates of the location.

What should be the height of transmitting antenna and the population covered if the television telecast is to cover a radius of $150 \mathrm{km}?$  The average population density around the tower is $2000 {\mathrm{km}}^{-2}$ and the value of $R_{\mathrm{e}}=6.5\times {10}^6 \mathrm{m}.$

During ground wave propagation earth behaves like a _____.

A TV tower has a height of $200 \mathrm{m}$. How much population is covered by the TV broadcast if the average population density around the tower is $1200 \mathrm{k}{\mathrm{m}}^{-2}$ (radius of the earth$=6.37\times {10}^6$ m)

A TV tower has a height of 100 m. How much population is covered by the TV broadcast if the average population density around the tower is $100 \mathrm{k}{\mathrm{m}}^{-2}$ (radius of the earth$=6.37\times {10}^6$ m)

A layer of ionosphere does not reflect waves with frequencies greater than 10 MHz; then maximum electron density in this layer is 

Ground waves are polarised in ______ direction.

The sky wave propagation is suitable for radio-waves of frequency

Long range radio transmission is possible when the radiowaves are reflected from the ionosphere. For this to happen the frequency of the radiowaves must be in the range :

The electric field of an electromagnetic wave travelling through vacuum is given by the equation$E=E_0\sin (kx-\omega t)$. The quantity that is independent of wavelength is