Find the rms electric field strength of a given EM wave

[henrco]

Hi,

I was able to correctly calculate the answer to part 1 below but the answer to part 2 is incorrect
and I cannot see the error of my ways... any help gratefully received.

1. Homework Statement
An electromagnetic wave has an intensity of 127 W/m2.

1) Find its rms electric field strength.
2) Find its rms magnetic field strength.

Homework Equations

Bo = Eo/c

Brms = B/sqr(2)

The Attempt at a Solution

Answer to part 1 : Eo = 219 V/m

Part 2

Calculate Bo = 219/2.998 x 10^8 = 7.3 x 10^-7

Brms = (7.3 x 10^-7)/sqr(2) = 5.17 x 10^-7 T

This answer for part 2, doesn't match the expected answer.

 

[TSny]

Does the answer to part 1 give E₀ or E_rms? How do you find B_rms from E_rms?

 

[henrco]

Thank you for replying and your question helped me understand my mistake.

Part 1's answer was Erms, and I was using this answer for part 2 instead of using Eo.
When I recalculated using the correct value I got the answer I expected.