electromagnetic-waves Question 16

Question: Q. 6. A plane electromagnetic wave of frequency 25 MHz travels in free space along the x-direction. At a particular point in space and time, E=

6.3j^ V/m. What is B at this point?

U] [SQP II 2017]

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Solution:

Ans. The magnitude of B is

B=Ec =6.3 V/m3×108 m/s =2.1×108 T

To find the direction, we note that E is along y-direction and the wave propagates along x-axis. Therefore, B should be in a direction perpendicular to both x and y-axes. Using vector algebra, E×B should be along x-direction.

Since, (+j^)×(+k^)=i^ so, B is along z-direction and is 2.1×108 T.

[CBSE Marking Scheme 2017]



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