CUET Preparation Today
In a plane electromagnetic wave electric field varies with time having an amplitude 1 Vm−1 . The frequency of wave is 0.5 × 1015 Hz. The wave is propagation along X-axis. What is the average energy density of magnetic field? |
1.1 × 10−12J m−3 2.2 × 10−12J m−3 3.3 × 10−12J m−3 4.4 × 10−12J m−3 |
4.4 × 10−12J m−3 |
The correct answer is Option 2: 2.2 × 10−12J m−3 Given: Electric field amplitude $E_0 = 1\text{ V m}^{-1}$. Constant: $\varepsilon_0 \approx 8.85 \times 10^{-12} \text{ C}^2\text{N}^{-1}\text{m}^{-2}$. The average energy density of the magnetic field ($u_B$) is calculated using the formula: $u_B = \frac{1}{4} \varepsilon_0 E_0^2$ $u_B = \frac{1}{4} \times (8.85 \times 10^{-12}) \times (1)^2$
$u_B = 2.21 \times 10^{-12} \text{ J m}^{-3}$ |
