# NCERT Physics Class 12 Exemplar Ch 8 Electromagnetic Waves Part 5

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Q 31 A plane EM wave travelling in vacuum along z direction is given by.

(i) Evaluate.Over the rectangular loop shown in Figure.

(ii) Evaluate. Over the surface bounded by loop 1234.

(iii) Use equation to prove

(iv) By using similar process and the equation

Ans:

For evaluating let us consider the rectangle 1234 to be made of strips of area each.

Using the relations obtained in Equations (1) and (2) and simplifying, we get

(iv) For evaluating , let us consider the loop 1234 in yz plane as shown in Fig

.

(3)

Now to evaluate , let us consider the rectangle 1234 to be made of strips of area *hdz *each.

(4)

In

Using relations obtained in Equations (3) and (4) and simplifying, we get