Question

A laser beam has intensity $I$. What is the amplitude of electric field in the beam?

• A. $\sqrt{\frac{I}{{\epsilon }_{0}C}}$
• B. $\sqrt{\frac{2I}{{\epsilon }_{0}C}}$
• C. $\sqrt{\frac{3I}{{\epsilon }_{0}C}}$
• D. $\sqrt{\frac{4I}{{\epsilon }_{0}C}}$

Answer 1

The correct option is B $\sqrt{\frac{2I}{{\epsilon }_{0}C}}$

Intensity of a laser beam is given by
$I=\frac{1}{2}{ϵ}_0{E}_0^{2}c$

$\Rightarrow E_0=\sqrt{\frac{2I}{{ϵ}_{0}C}}$