The intensity of an electromagnetic wave is
I=21ϵ0cE02.
From the relation E0=cB0, we get I=21ϵ0c3B02.
Solving for magnetic field amplitude:
B0=ϵ0c32I=8.85×10−12×(3×108)32×4.0×1014=2.39×10148.0×1014
=3.347=1.83 T.
JEE Main 2026 — Physics Electromagnetism
A laser beam has intensity of 4.0×1014 W/m2. The amplitude of magnetic field associated with beam is ____ T.
(Take ϵo=8.85×10−12C2/Nm2 and c=3×108 m/s)
Held on 22 Jan 2026 · Verified 6 Jul 2026.
18.3
1.83
5.5
2.0
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