Electromagnetic Waves Class 12 Case Study Questions Physics Chapter 8

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Last Updated on December 26, 2024 by XAM CONTENT

Hello students, we are providing case study questions for class 12 physics. Case study questions are the new question format that is introduced in CBSE board. The resources for case study questions are very less. So, to help students we have created chapterwise case study questions for class 12 physics. In this article, you will find case study questions for cbse class 12 physics chapter 8 Electromagnetic Waves.

Chapter	Electromagnetic Waves
Type of Questions	Case Study Questions
Nature of Questions	Competency Based Questions
Board	CBSE
Class	12
Subject	Physics
Unit	Unit 5 Electromagnetic Waves
Useful for	Class 12 Studying Students
Answers provided	Yes
Difficulty level	Mentioned
Important Link	Class 12 Physics Chapterwise Case Study

Case Study Questions on Electromagnetic Waves

Questions

Question 1:

A stationary charge produces only an electrostatic field while a charge in uniform motion produces a magnetic field, that does not change with time. An oscillating charge is an example of accelerating charge. It produces an oscillating magnetic field, which in turn produces an oscillating electric field and so on. The oscillating electric and magnetic fields regenerate each other as a wave which propagates through space.

Read the given passage carefully and give the answer of the following questions:

Q 1. Magnetic field in a plane electromagnetic wave is given by $\vec{B}=B_0 \sin (k x+\omega t) \hat{j} T$. What will be the expression for corresponding electric field?

Q 2. The electric field component of monochromatic radiation is given by $\frac{d E}{d z}=-2 E_0 k \sin k z \cdot \cos \omega t$. What will be its magnetic field component?

Q 3. A plane electromagnetic wave of frequency 25 MHz travels in a free space along $X$-direction. At a particular point in space and time, $E=(6.3 \hat{j}) \mathrm{V} / \mathrm{m}$. What is magnetic field at that time?

Q 4. A plane electromagnetic wave travelling along the $X$-direction has a wavelength of 3 mm . The variation in the electric field occurs in the $Y$-direction with an amplitude $66 \mathrm{~V} \mathrm{~m}^{-1}$. Write the equations for the electric and magnetic fields as a function of $x$ and $t$.

Answers

1. Given, $\overrightarrow{\mathrm{B}}=B_0 \sin (k x+\omega t) \hat{\mathrm{j}} T$

The relation between electric and magnetic fields is, $C=\frac{E}{B}$ or $E=C B$
The electric field component is perpendicular to the direction of propagation and the direction of magnetic field. Therefore, the electric field component along Z-axis is obtained as $\vec{E}=c B_0 \sin (k x+\omega t) \hat{k} k V / m$.

2. Since,
\[
\frac{d E}{d z} = -\frac{d B}{d t}
\]
\[
\frac{d E}{d z} = -2 E_0 k \sin k z \cos \omega t = -\frac{d B}{d t}
\]
\[
d B = +2 E_0 k \sin k z \cos \omega t \, d t
\]
\[
B = +2 E_0 k \sin k z \int \cos \omega t \, d t = +2 E_0 \frac{k}{\omega} \sin k z \sin \omega t
\]

\[
\because \frac{E_0}{B_0} = \frac{\omega}{k} = c
\]

\[
\therefore \quad B = \frac{2 E_0}{c} \sin k z \sin \omega t
\]
Thus, the magnetic field component is:
\[
\vec{B} = \frac{2 E_0}{c} \sin k z \sin \omega t \hat{i}
\]

3. Given, $E=6.3 \hat{\mathrm{i}} \mathrm{V} / \mathrm{m}, c=3 \times 10^8 \mathrm{~m} / \mathrm{s}$

The magnitude of magnetic field,

$$
B_z=\frac{E}{C}=\frac{6.3}{3 \times 10^8}=2.1 \times 10^{-8} \mathrm{~T}=0.021 \mu \mathrm{~T}
$$

4. Given, $E_0=66 \mathrm{Vm}^{-1}, E_y=66 \cos \omega\left(t-\frac{x}{c}\right)$,

$$
\begin{aligned}
\lambda=3 \mathrm{~mm}=3 \times 10^{-3} \mathrm{~m}, k=\frac{2 \pi}{\lambda} \\
\frac{\omega}{k}=c \Rightarrow \omega=c k=3 \times 10^8 \times \frac{2 \pi}{3 \times 10^{-3}}
\end{aligned}
$$

or $\omega=2 \pi \times 10^{11} \mathrm{rad} / \mathrm{s}$

$$
\begin{aligned}
\therefore \quad E_y & =66 \cos 2 \pi \times 10^{11}\left(t-\frac{x}{c}\right) \\
B_z & =\frac{E_y}{c}=\left(\frac{66}{3 \times 10^8}\right) \cos 2 \pi \times 10^{11}\left(t-\frac{x}{c}\right) \\
& =2.2 \times 10^{-7} \cos 2 \pi \times 10^{11}\left(t-\frac{x}{c}\right)
\end{aligned}
$$

Also check

Case study questions for other chapters of class 12 physics is given below.

• Semiconductor Electronics Class 12 Case Study Questions Physics Chapter 14
• Nuclei Class 12 Case Study Questions Physics Chapter 13
• Atoms Class 12 Case Study Questions Physics Chapter 12
• Dual Nature of Radiation and Matter Class 12 Case Study Questions Physics Chapter 11
• Wave Optics Class 12 Case Study Questions Physics Chapter 10
• Ray Optics and Optical Instruments Class 12 Case Study Questions Physics Chapter 9
• Electromagnetic Waves Class 12 Case Study Questions Physics Chapter 8
• Alternating Current Class 12 Case Study Questions Physics Chapter 7
• Electromagnetic Induction Class 12 Case Study Questions Physics Chapter 6
• Magnetism and Matter Class 12 Case Study Questions Physics Chapter 5
• Moving Charges and Magnetism Class 12 Case Study Questions Physics Chapter 4
• Current Electricity Class 12 Case Study Questions Physics Chapter 3
• Electrostatic Potential and Capacitance Class 12 Case Study Questions Physics Chapter 2
• Electric Charges and Fields Class 12 Case Study Questions Physics Chapter 1
• Case Study Questions for Class 12 Physics

We hope the given case study questions for Electromagnetic Waves Class 12 helps you in your learning.

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• Chapter Test for Class 12 Physics with Solutions
• 230 Important Numerical for Class 12 Physics
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Topics from which case study questions may be asked

• Basic Idea of Displacement Current
• Electromagnetic Waves
• Characteristics of Electromagnetic Waves
• Transverse Nature of Electromagnetic Waves (Qualitative Idea)
• Electromagnetic Spectrum
  • Radio Waves
  • Microwaves
  • Infrared
  • Visible Light
  • Ultraviolet
  • X-rays
  • Gamma Rays
• Uses of Electromagnetic Waves

Two electric field lines never cross each other. If they intersect, then there will be two directions of electric field at the point of intersection which is not possible.

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