Question 140: EM waves

Question

A 27 mW laser beam has a cross-sectional area of 10 mm
2
. The magnitude of the maximum electric field in this electromagnetic wave is given by :
[Given permittivity of space $ \in $
0
= 9 $ 	imes $ 10
–12
SI units, Speed of light c = 3 $ 	imes $ 10
8
m/s]

Accepted Answer

Intensity of EM wave is given by
${m I} = {{Power} \over {Area}} = {1 \over 2}{\varepsilon _0}E_0^2C$
$ = {{27 	imes {{10}^{ - 3}}} \over {10 	imes {{10}^{ - 6}}}}$
$ = {1 \over 2} 	imes 9 	imes {10^{ - 12}} 	imes {E^2} 	imes 3 	imes {10^8}$
$E = \sqrt 2  	imes {10^3}kv/m$
$ = 1.4$ kv/m

Answer

2 kV/m

Answer

1 kV/m

Answer

1.4 kV/m

Answer

0.7 kV/m

EM waves

A 27 mW laser beam has a cross-sectional area of 10 mm 2 . The magnitude of the maximum electric field in this electromagnetic wave is given by : [Given permittivity of space \in 0 = 9 \times 10 –12 SI units, Speed of light c = 3 \times 10 8 m/s]

Choose the correct answer: