Question

If the electric field associated with a radiation of frequency 10MHz is E = 10 sin(kx – ωt)mV/m then its energy density is _______ Jm^–3(ε_o = 8.85 × 10^–12C²N^–1m^–2)

(A) 4.425 × 10^–10

(B) 6.26 × 10^–14

(C) 8.85 × 10^–16

(D) 8.85 × 10^–14

Answer 1

The correct option is (A) 4.425 × 10^–10.

Explanation:

f = 10MHz = 10 × 10⁶Hz = 10⁷Hz

E = 10 sin(kx – ωt)

Hence E_o = 10

Total energy density = (1/2)ε_oE_o²

= (1/2) × 8.85 × 10^–12 × (10)²

= 4.425 × 10^–10 J/m³