Question

A 27 mW laser beam has a cross-sectional area of 10 mm². The magnitude of the maximum electric field in this electromagnetic wave is given by:

[Given permittivity of space ∈₀ = 9 × 10^-12 SI units, Speed of light c = 3  10⁸ m/s] 

पर्याय

• 2 kV/m

• 0.7 kV/m

• 1 kV/m

• 1.4 kV/m

Answer 1

1.4 kV/m

Explanation:

EM wave intensity 

⇒ I = `"Power"/"Area" = 1/2 epsilon_0"E"_0^2"c"`

[where E₀ = maximum electric field]

⇒ `(27xx10^-3)/(10xx10^-6) = 1/2xx9xx10^-12xx"E"_0^2xx3xx10^8`

⇒ E₀ = `sqrt2xx10^3` kV/m

= 1.4 kV/m