Electromagnetic Waves Chapter-Wise Test 18

Correct answer Carries: 4.

Wrong Answer Carries: -1.

Why do electromagnetic waves not require a medium for propagation?

Electromagnetic waves are self-sustaining oscillations of electric and magnetic fields, where a changing electric field generates a magnetic field and vice versa, requiring no material medium.

They are self-sustaining field oscillations
They travel slower in vacuum
They rely on charged particles
They depend on mechanical vibrations
1

Why are ultraviolet rays used in sterilization processes?

Ultraviolet rays have high energy due to their short wavelengths, allowing them to disrupt molecular bonds in microorganisms, effectively killing them for sterilization purposes.

Low energy absorption
High energy disruption
Thermal heating
Visible light emission
2

Which frequency range corresponds to short wave bands used in radio communication?

The document states that frequencies up to \( 54 \, \text{MHz} \) are used for short wave bands in radio communication.

\( 88 \, \text{MHz} \) to \( 108 \, \text{MHz} \)
\( 530 \, \text{kHz} \) to \( 1710 \, \text{kHz} \)
Up to \( 54 \, \text{MHz} \)
\( 4 \times 10^{14} \, \text{Hz} \) to \( 7 \times 10^{14} \, \text{Hz} \)
3

An electromagnetic wave in vacuum has an angular frequency \( \omega = 4 \times 10^{11} \, \text{rad/s} \). What is its frequency in Hz?

Frequency \( v = \frac{\omega}{2\pi} \). Given \( \omega = 4 \times 10^{11} \, \text{rad/s} \), \( v = \frac{4 \times 10^{11}}{2 \pi} \approx 6.37 \times 10^{10} \, \text{Hz} \).

\( 4 \times 10^{10} \, \text{Hz} \)
\( 5 \times 10^{10} \, \text{Hz} \)
\( 6.37 \times 10^{10} \, \text{Hz} \)
\( 8 \times 10^{10} \, \text{Hz} \)
3

An electromagnetic wave in vacuum has a magnetic field amplitude of \( B_0 = 2 \times 10^{-8} \, \text{T} \). What is the electric field amplitude? (Given \( c = 3 \times 10^8 \, \text{m/s} \))

Using \( E_0 = B_0 c \), we have \( E_0 = (2 \times 10^{-8}) \times (3 \times 10^8) = 6 \, \text{V/m} \).

3 V/m
4 V/m
5 V/m
6 V/m
4

Why are microwaves suitable for radar systems in aircraft navigation?

The document explains that microwaves have short wavelengths, making them suitable for radar systems as they can form narrow beams for precise detection.

They have long wavelengths
They have short wavelengths
They are absorbed by the atmosphere
They travel slower than other waves
2

Why does exposure to UV radiation cause tanning of the skin?

The document explains that exposure to UV radiation induces the production of more melanin, which causes tanning of the skin.

It heats the skin
It emits visible light
It causes water molecules to vibrate
It induces production of melanin
4

In electromagnetic theory, what explains the constant speed of light in vacuum across all frequencies?

The speed of light in vacuum is determined by the fundamental constants of permittivity (\( \varepsilon_0 \)) and permeability (\( \mu_0 \)), independent of frequency, as \( c = \frac{1}{\sqrt{\mu_0 \varepsilon_0}} \).

Frequency variation
Wavelength dependence
Energy absorption
Fundamental constants
4

What is the approximate wavelength range of infrared waves as per the document?

The document states that infrared waves range from \( 1 \, \text{mm} \) to \( 700 \, \text{nm} \).

\( > 0.1 \, \text{m} \)
\( 0.1 \, \text{m} \) to \( 1 \, \text{mm} \)
\( 400 \, \text{nm} \) to \( 0.6 \, \text{nm} \)
\( 1 \, \text{mm} \) to \( 700 \, \text{nm} \)
4

Which of the following statements about the electromagnetic spectrum is true?

The document explains that the boundaries between different regions of the electromagnetic spectrum are not sharply defined, and there are overlaps.

Each region has a fixed wavelength
All waves travel at different speeds
Regions are sharply divided
Boundaries are not sharply defined
4

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