# Amplitude of oscillating magnetic field

#### Roodles01

N = 1/2 E0 √(ε/μ)
so
E0 = √2*N*(ε/μ)
where the value of ε/μ is 376.7Ω

I have a similar question to this, below, regarding amplitude of an oscillating magnetic field.
Yes, I'd like the answer, but am initially stuck deciding whether the mW is milli- or mega-

2. Homework Equations
A laser found in supermarket checkout scanners emits light in a 1.1 mm diameter beam with a power of 1.3 mW.

Part A
What is the amplitude of the oscillating electric field in the laser beam?
Express your answer to two significant figures and include the appropriate units.
=

Part B
What is the amplitude of the oscillating magnetic field in the laser beam?
Express your answer to two significant figures and include the appropriate units

Part A
N = 1/2 E0 √(ε/μ)
so
E0 = √2*N*(ε/μ)
where the value of ε/μ is 376.7Ω
E0 = √2*103*376.7Ω
= 877.0 V m-2

Not sure how to find the amplitude of the oscillating magnetic field though.