question_answer

A 27 mW laser beam has a cross-sectional area of\[10\text{ }m{{m}^{2}}\]. The magnitude of the maximum electric field in this electromagnetic wave is given by [Given permittivity of space\[{{\varepsilon }_{0}}=9\times {{10}^{-12}}\] SI units, speed of light \[c=3\times {{10}^{8}}m/s\]] [JEE Main 11-Jan-2019 Evening]

A) 2 kV/m

B) 0.7 kV/m

C) 1 kV/m

D) 1.4 kV/m

Correct Answer: D

Solution :

[d] Intensity of electromagnetic wave is given by