Optics | Amplitude of Electric Field Given Radiant Flux Density

[heycoa]

Homework Statement

A laser provides pulses of EM radiation in vacuum lasting 7.47* 10-12 s. If the radiant flux
density is 2.65 * 1020 W/m2, determine the amplitude of the electric field (x *1011) of the beam. Units are required as listed in instructions.

Homework Equations

Irradiance = c*ε₀/2 * E₀²

The Attempt at a Solution

If I solve for E₀, I end up with: 4.47*10¹¹ V/m². My question is that I did not use the time that the question gave me. All I did was plug into the irradiance equation and solve for E₀. Is this correct?

 

[mark726]

Yes, your approach is correct. The irradiance equation only requires the electric field amplitude (E0) and the speed of light (c) to calculate the radiant flux density. The time given in the question is not needed for this calculation. Therefore, your answer of 4.47*1011 V/m2 is correct.