Question

The amplitude of electric field in a parallel beam of light of intensity $4\, Wm ^{-2}$ is

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

Answer 1

Answer: (D)

As, $I=\frac{1}{2} \varepsilon_{0} E_{0}^{2} C$
or $E_{0}=\sqrt{\frac{2 I}{\varepsilon_{0} C}}=\sqrt{\frac{2 \times 4}{\left(8.85 \times 10^{-12}\right) \times\left(3 \times 10^{8}\right)}}$
$=55.5\, NC ^{-1}$