Verified Solution • 2025–26 Session moderate

QPages 338-339: Q7: HC Verma: Concepts of Physics - Volume 2 Electromagnetic Waves Pages 338-339: Q7 Solution: Consider the following two statements regarding a linearly…

⚠️ Common Exam Traps & Conceptual Pitfalls

Students often mistake the phrase “average value” for the field amplitudes and assume $\langle E\rangle=\langle B\rangle$ because $B=E/c$. In a sinusoidal wave the time‑average of $E$ and $B$ over a period is zero, while the time‑averaged energy densities $\langle \tfrac12\varepsilon_0E^2\rangle$ and $\langle \tfrac12\mu_0^{-1}B^2\rangle$ are equal. Remember to distinguish between the arithmetic mean of the field (zero) and the mean of its square (non‑zero, equal for electric and magnetic parts).

Consider the following two statements regarding a linearly polarised, plane electromagnetic wave : A) The electric field and the magnetic field have equal average values. B) The electric energy and the magnetic energy have equal average values.

Multiple Choice Options

  • A Both A and B are true.
  • B A is false but B is true.
  • C B is false but A is true
  • D Both A and B are false.

Step-by-Step Verified Solution

**Answer:** (b) A is false but B is true. **Step-by-Step Explanation:** The average values of E and B are zero, not equal (A false). The average electric and magnetic energy densities are equal (B true).

All Questions in this Chapter

QPage 338: Q1 QPage 338: Q2 QPage 338: Q3 QPage 338: Q4 QPage 338: Q5 QPage 338: Q6 QPage 338: Q7 QPage 339: Q1 QPage 339: Q1 QPage 339: Q2 QPage 339: Q2 QPage 339: Q3 QPage 339: Q3 QPage 339: Q4 QPage 339: Q4 QPage 339: Q5 QPage 339: Q5 QPage 339: Q6 QPage 339: Q7 QPage 339: Q8 QPage 339: Q9 QPages 338-339: Q1 QPages 338-339: Q2 QPages 338-339: Q3 QPages 338-339: Q4 QPages 338-339: Q5 QPages 338-339: Q6 QPages 338-339: Q7 QPages 338-339: Q8 QPages 338-339: Q9

Related Learning Resources & Exam Preparation

Chapter Practice Bank
Practice all topic-wise questions from Electromagnetic Waves
Reference Textbook Solutions
Explore complete chapter exercises for HC Verma: Concepts of Physics - Volume 2
Competitive PYQ Question Bank
Browse year-wise authentic previous years' questions with solutions
Authentic CBT Mock Tests
Simulate official exam environment with live timer and percentile scoring