Question

Find the amplitude of the electric field in a parallel beam of light of intensity $2.0W{m}^{-2}$

• A. $28.5N{C}^{-1}$
• B. $38.8N{C}^{-1}$
• C. $43.2N{C}^{-1}$
• D. $31.9N{C}^{-1}$

Answer 1

The correct option is B $38.8N{C}^{-1}$

We can say intesity as
$I=U_{av}\times c$
where
$U_{av}=$energy density$=\frac{1}{2}{\epsilon }_0{E}_0^2$
$c=$speed of light
$\therefore E_0=\sqrt{\frac{2I}{c{\epsilon }_0}}$
By putting the value given we get
$E_0=38.8{\text{NC}}^{-1}$