Question

The amplitude of electric field in a parallel beam of light of intensity $4W{m}^{-2}$ is

• A. $40.5N{C}^{-1}$
• B. $45.5N{C}^{-1}$
• C. $50.5N{C}^{-1}$
• D. $55.5N{C}^{-1}$

Answer 1

Answer: (D)

As, $I=\frac{1}{2}{\epsilon }_0{E}_0^{2}C$
or $E_0=\sqrt{\frac{2I}{{\epsilon }_{0}C}}=\sqrt{\frac{2\times 4}{\left(8.85\times 10^{-12}\right)\times \left(3\times 10^8\right)}}$
$=55.5N{C}^{-1}$