Electromagnetic Waves Chapter-Wise Test 19

Correct answer Carries: 4.

Wrong Answer Carries: -1.

An electromagnetic wave in vacuum has an electric field amplitude of \( 90 \, \text{V/m} \). What is the magnetic field amplitude? (Given \( c = 3 \times 10^8 \, \text{m/s} \))

Using \( B_0 = \frac{E_0}{c} \), we have \( B_0 = \frac{90}{3 \times 10^8} = 3 \times 10^{-7} \, \text{T} \).

\( 1.5 \times 10^{-7} \, \text{T} \)
\( 2 \times 10^{-7} \, \text{T} \)
\( 2.5 \times 10^{-7} \, \text{T} \)
\( 3 \times 10^{-7} \, \text{T} \)
4

What is the significance of the equation \( \oint \mathbf{E} \cdot \mathrm{d} \mathbf{l} = -\frac{d \Phi_B}{dt} \) in Maxwell's equations?

This is Faraday's Law, which states that a changing magnetic flux induces an electric field, a key mechanism for electromagnetic wave propagation.

It describes the induction of an electric field by changing magnetic flux
It describes the induction of a magnetic field by changing electric flux
It states that magnetic monopoles exist
It relates electric flux to charge
1

Why are visible light waves critical for human vision?

Visible light waves have wavelengths that the human eye’s photoreceptors can detect, triggering neural responses that allow perception of color and detail in the environment.

High energy
Thermal effects
Long wavelength
Detectable wavelengths
4

What is the primary source of a magnetic field as per Maxwell's generalization?

Maxwell generalized Ampere's circuital law by introducing displacement current. According to this, the source of a magnetic field is not only the conduction current but also the time-varying electric field (displacement current).

Only conduction current
Only stationary charges
Both conduction current and time-varying electric field
Only magnetic monopoles
3

What is the typical wavelength range of radio waves according to the document?

The document mentions that radio waves have wavelengths greater than \( 0.1 \, \text{m} \), with long radio waves extending up to \( 10^6 \, \text{m} \).

\( 1 \, \text{mm} \) to \( 700 \, \text{nm} \)
\( > 0.1 \, \text{m} \)
\( 400 \, \text{nm} \) to \( 0.6 \, \text{nm} \)
\( 10^{-10} \, \text{m} \) to \( 10^{-14} \, \text{m} \)
2

The ozone layer protects the Earth by absorbing which type of electromagnetic waves?

The document mentions that the ozone layer absorbs most ultraviolet (UV) radiation, protecting life on Earth.

Infrared waves
Visible light
Ultraviolet rays
Radio waves
3

What type of charges produce electromagnetic waves according to the document?

The document mentions that accelerated charges, such as those oscillating or in non-uniform motion, produce electromagnetic waves.

Accelerated charges
Stationary charges
Uniformly moving charges
Charges at rest
1

What is the wavelength range of ultraviolet rays as per the electromagnetic spectrum?

The document states that ultraviolet rays range from about \( 400 \, \text{nm} \) to \( 0.6 \, \text{nm} \).

\( 1 \, \text{mm} \) to \( 700 \, \text{nm} \)
\( 400 \, \text{nm} \) to \( 0.6 \, \text{nm} \)
\( 10 \, \text{nm} \) to \( 10^{-4} \, \text{nm} \)
\( 700 \, \text{nm} \) to \( 400 \, \text{nm} \)
2

What type of charges produce electromagnetic waves as per the document?

The document states that accelerated charges radiate electromagnetic waves, not stationary or uniformly moving charges.

Accelerated charges
Stationary charges
Charges moving with uniform velocity
Charges at rest in a magnetic field
1

A parallel plate capacitor with plate area \( A = 0.02 \, \text{m}^2 \) and separation \( d = 5 \, \text{mm} \) is connected to a circuit with a current of \( 2 \, \text{A} \). What is the rate of change of electric flux between the plates? (Given \( \varepsilon_0 = 8.85 \times 10^{-12} \, \text{F/m} \))

Displacement current \( i_d = \varepsilon_0 \frac{d \Phi_E}{dt} \). For a capacitor, \( i_d = i \). Given \( i = 2 \, \text{A} \), we have \( \frac{d \Phi_E}{dt} = \frac{i}{\varepsilon_0} = \frac{2}{8.85 \times 10^{-12}} \approx 2.26 \times 10^{11} \, \text{Vm/s} \).

\( 2.26 \times 10^{11} \, \text{Vm/s} \)
\( 1.13 \times 10^{11} \, \text{Vm/s} \)
\( 4.52 \times 10^{11} \, \text{Vm/s} \)
\( 5.65 \times 10^{11} \, \text{Vm/s} \)
1

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