किसी विद्युत चुम्बकीय तरंग में विधुत क्षेत्र निम्नवत है  \(\overrightarrow{\mathrm{E}}=20 \sin \omega\left(\mathrm{t}-\frac{\mathrm{x}}{\mathrm{c}}\right) \overrightarrow{\mathrm{j} N C^{-1}}\) जहाँ \(\omega\) एवं \(\mathrm{c}\) क्रमशः कोणीय आवृत्ति एवं विद्युत चुम्बकीय तरंग का वेग हैं। \(5 \times 10^{-4} \mathrm{~m}^3\) के आयतन में अंतर्विष्ट (Contained) ऊर्जा होगी: (दिया है \(\varepsilon_0=8.85 \times 10^{-12} \mathrm{C}^2 / \mathrm{Nm}^2\) )

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.