Question: Q. 15. For a plane electromagnetic wave, propagating along the $z$-axis, write the two (possible) pairs of expressions for its oscillating electric and magnetic fields. How are the peak values of these (oscillating) fields related to each other?
U] [Foreign 2016]
Show Answer
Solution:
Ans. For the EM wave, propagating along the $z$-axis, we have
$E=E_{0} \sin (k z \mp \omega t)$ and $B=B_{0} \sin (k z \mp \omega t) \quad 1 / 2$
The two possible forms are :
| $E_{x}=E_{0} \sin (k z-\omega t)$ | $1 / 2$ | |
|---|---|---|
| And | $B_{y}=B_{0} \sin (k z-\omega t)$ | |
| We have, | $E_{y}=E_{0} \sin (k z+\omega t)$ | $1 / 2$ |
| $B_{x}=B_{0} \sin (k z+\omega t)$ | ||
| $E_{0}=c B_{0}$ | $1 / 2$ |
[Do not deduct any mark if the student uses any of the two signs ( - or + ) in the two sets of expression.]
[CBSE Marking Scheme 2016]
Short Answer Type Questions-II
(3 marks each)
