Question

The rms value of electric field of light coming from sun is 720 N/c. The average total energy density of electromagnetic wave is _______. 

(A) 6.37 × 10^–9J/m³ 

(B) 4.58 × 10^–6J/m³ 

(C) 81.35 × 10^–12J/m³ 

(D) 3.3 × 10^–3J/m³

Answer 1

The correct option is (B) 4.58 × 10^–6J/m³.

Explanation:

Total average energy = εoE_rms² 

= 8.85 × 10^–12 × (720)² 

= 4.58 × 10^–6J/m³