Eduprobe

Question:

An electromagnetic wave is represented by the electric field E⃗ = E₀ n̂sin[ωt + (6y - 8z)]. Taking unit vectors in x, y and z directions to be î, ĵ, k̂, the direction of propagation ŝ, is:

ŝ=4ĵ-3k̂

ŝ=(-3ĵ+4k̂)

ŝ=3î-4ĵ

ŝ=(-4k̂+3ĵ)

Solution:

Correct option is C. ŝ=(-3ĵ+4k̂)
E=E₀n̂sin(ωt+(6y-8z))=E₀n̂sin(ωt+k⃗.r⃗) where r⃗=xî+yĵ+zk̂ and k⃗.r⃗=6y-8z ⇒k⃗=6ĵ-8k̂
direction of propagation ŝ=-k̂ ŝ=(-3ĵ+4k̂)