Electromagnetic Waves & Spectrum Test - 3

Explanation:

• Maxwell 's equations describe how electric and magnetic fields interact with each other.


• One of Maxwell 's equations states that a time-varying magnetic field acts as a source of electric field.


• This means that when a magnetic field changes over time, it induces an electric field in the surrounding space.


• Similarly, another Maxwell 's equation states that a time-varying electric field acts as a source of magnetic field.


• Therefore, time-varying magnetic fields and time-varying electric fields are interconnected and can generate each other.


 

Radio waves have frequencies as high as 300 gigahertz (GHz) to as low as 30 hertz (Hz). Like all other electromagnetic waves, radio waves travel at the speed of light in vacuum (and close to the speed of light in the Earth 's atmosphere, which acts as the transmission media for the vast majority of terrestrial use).
 

The electromagnetic wave travels in vacuum along z-direction. Then, the electric field vector and magnetic field vector will be in the XY plane.
Frequency of the wave = 30 MHz
Converting into Hz, v = 30 ×10⁶ Hz.
speed of light, c = 3 ×10⁸ m/s
Wavelength of the wave can be calculated using the following relation:
λ= c/v
⇒λ= 3 ×10⁸ /30 ×10⁶
⇒λ= 10 m

The frequency of radiation arising from the two close energy levels in hydrogen known as Lamb shift i.e. 1057 MHz is radio waves as it belongs to the short wavelength end of the electromagnetic spectrum.

The frequency of radiation arising from the two close energy levels in hydrogen known as Lamb shift i.e. 1057 MHz is radio waves as it belongs to the short wavelength end of the electromagnetic spectrum. this wavelength correspond to microwave region of electromagnetic waves.

Long distance radio broadcasts use short-wave bands because they can be reflected by the ionosphere of the earth 's atmosphere and thus can be send to longer distances.

The electromagnetic waves are produced by vibration of an electric charge. This creates a wave which is both as electric and magnetic components. This way oscillates in perpendicular planes with respect to each other and in a phase.This creates all electromagnetic waves begin with an oscillating charged particle which creates an oscillating electric and magnetic field.

Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter; with frequencies between 300 MHz (1 m) and 300 GHz (1 mm). Different sources define different frequency ranges as microwaves; the above broad definition includes both UHF and EHF (millimeter wave) bands.
Answer B and D both are correct.

Magnetic field part of a harmonic electromagnetic wave in vacuum
,B₀ ​=510 ×10⁻⁹ T
Speed of light,
C=3 ×10⁸ m/s
E=cB_o ​=153N/C

TV signals being of high frequency are not reflected by the ionosphere. Therefore, to reflect these signals, satellites are needed. That is why, satellites are used for long distance TV transmission.
 Most long-distance shortwave (high frequency) radio communication —between 3 and 30 MHz —is a result of skywave propagation.
This 3-30 MHz is a range of frequencies which are used in sky waves propagation so that the ionosphere is capable of reflecting it.