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Question:

The magnetic field of a plane electromagnetic wave is given by: B = B₀[cos(kz - ωt)] + B₁[cos(kz + ωt)], where B₀ = 3 × 10⁻⁵ T; B₁ = 2 × 10⁻⁶ T. The rms value of the force experienced by a stationary charge Q = 10⁻⁴ C at z = 0 is closest to:

0.9N

0.1N

3 × 10⁻² N

0.6N

Solution:

Correct option is D. 0.6N
Maximum Electric field E = (B)(c)
E⃗₀ = (3 × 10⁻⁵)c(-j^)
E⃗₁ = (2 × 10⁻⁶)c(-i^)
Maximum force F⃗net = qE⃗ = qc(3 × 10⁻⁵j^ - 2 × 10⁻⁶i^)
F₀max = 10⁻⁴ × 3 × 10⁸
(Frms = F₀/√2 = 0.6N