In a plane electromagnetic wave, the directions of electric field and magnetic field are represented by k and 2i-2j, respectively. What is the unit vector along direction of propagation of the wave? (a) 1/√(5)(i+2j) (b) 1/√(5)(2i+j) (c) 1/√(2)(i+j) (d) 1/√(2)(j+k)

Answer: (c). Propagation direction is along E. k×(2i-2j) = 2j + 2i. Unit vector: (2i+2j)/(2√(2)) = 1/√(2)(i+j). So the answer is (c).

In a plane electromagnetic wave, the directions of electric field and… | JEE Main 2020 (2 Sep, Shift 2)

Q49JEE Main 2020 · 2 SEP · SHIFT 2Easy

Nature of EM Waves & Wave Equation

In a plane electromagnetic wave, the directions of electric field and magnetic field are represented by $\hat{k}$ and $2\hat{i}-2\hat{j}$ , respectively. What is the unit vector along direction of propagation of the wave?

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Answer: (c)

Propagation direction is along $\vec{E}\times\vec{B}$ .
$\hat{k}\times(2\hat{i}-2\hat{j}) = 2\hat{j} + 2\hat{i}$ .
Unit vector: $\frac{2\hat{i}+2\hat{j}}{2\sqrt{2}} = \frac{1}{\sqrt{2}}(\hat{i}+\hat{j})$ .
So the answer is (c).

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Nature of EM Waves & Wave Equation question from JEE Main 2020 (2 Sep, Shift 2)

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