Electromagnetic Waves Chapter-Wise Test 5

Correct answer Carries: 4.

Wrong Answer Carries: -1.

Infrared waves are often called heat waves because:

Infrared waves are absorbed by water molecules in materials, increasing their thermal motion and thus heating the material.

They have the highest frequency
They cause vibration of atoms and molecules, increasing temperature
They are produced by cold bodies
They are not absorbed by any material
2

An electromagnetic wave in vacuum has a frequency of \( 30 \, \text{MHz} \). What is its wavelength? (Given \( c = 3 \times 10^8 \, \text{m/s} \))

Using \( v \lambda = c \), we have \( \lambda = \frac{c}{v} = \frac{3 \times 10^8}{30 \times 10^6} = 10 \, \text{m} \).

5 m
10 m
15 m
20 m
2

What is the significance of Maxwell's displacement current in the context of electromagnetic waves?

The document explains that displacement current leads to the generation of a magnetic field from a changing electric field, which, combined with Faraday's law, results in the propagation of electromagnetic waves.

It enables the propagation of electromagnetic waves
It cancels out conduction current
It eliminates the need for magnetic fields
It only affects stationary charges
1

What property of infrared waves makes them suitable for physical therapy applications?

Infrared waves are absorbed by tissues, increasing thermal motion and heating the area, which promotes blood flow and relaxation in physical therapy.

Their high frequency
Their visible spectrum
Their ability to heat tissues
Their penetrating power
3

Which electromagnetic waves are produced by the vibration of atoms and molecules?

Infrared waves are produced by the vibration of atoms and molecules, as mentioned in the document.

Radio waves
Microwaves
Infrared waves
Ultraviolet waves
3

The velocity of light in a medium with permittivity \( \varepsilon \) and permeability \( \mu \) is:

As per Maxwell's equations, the velocity of light in a medium is \( v = \frac{1}{\sqrt{\mu \varepsilon}} \).

\( \frac{1}{\sqrt{\mu_0 \varepsilon_0}} \)
\( \frac{1}{\sqrt{\mu \varepsilon}} \)
\( \sqrt{\mu \varepsilon} \)
\( \sqrt{\mu_0 \varepsilon_0} \)
2

An electromagnetic wave has a wave number \( k = 0.5 \, \text{rad/m} \). What is its wavelength in vacuum?

The wave number \( k = \frac{2 \pi}{\lambda} \). Given \( k = 0.5 \, \text{rad/m} \), we have \( \lambda = \frac{2 \pi}{k} = \frac{2 \pi}{0.5} \approx 12.56 \, \text{m} \).

6.28 m
12.56 m
18.84 m
25.12 m
2

What significant prediction emerged from Maxwell's equations regarding wave propagation?

The document highlights that Maxwell's equations predicted the existence of electromagnetic waves, which are time-varying electric and magnetic fields that propagate in space.

Existence of electromagnetic waves
Static electric fields
Magnetic monopoles
No wave propagation
1

What is one precaution welders take to protect their eyes from UV radiation?

The document mentions that welders wear special glass goggles or face masks to protect their eyes from the large amounts of UV radiation produced by welding arcs.

Wear ordinary sunglasses
Use visible light filters
Avoid using any protection
Wear special glass goggles
4

In electromagnetic wave theory, what is the relationship between the electric and magnetic field amplitudes in vacuum?

The electric and magnetic field amplitudes are related by the speed of light in vacuum, where \( E_0 = B_0 c \), or equivalently \( B_0 = \frac{E_0}{c} \), ensuring energy balance in the wave.

\( E_0 = B_0 \)
\( E_0 = B_0 c \)
\( B_0 = E_0 c^2 \)
\( E_0 = B_0 / c^2 \)
2

Performance Summary

Score:

Category Details
Total Attempts:
Total Skipped:
Total Wrong Answers:
Total Correct Answers:
Time Taken:
Average Time Taken per Question:
Accuracy:
0