Optics Question 305
Question: An electromagnetic wave travels along z-axis. Which of the following pairs of space and time varying fields would generate such a wave
[CBSE PMT 1994]
Options:
A) $ E _{x},B _{y} $
B) $ E _{y},B _{x} $
C) $ E _{z},B _{x} $
D) $ E _{y},B _{z} $
Show Answer
Answer:
Correct Answer: A
Solution:
$ E _{x} $ and $ B _{y} $ would generate a plane EM wave travelling in z-direction. $ \vec{E} $ , $ \vec{B} $ and $ \vec{k} $ form a right handed system $ \vec{k} $ is along z-axis. As $ \hat{i}\times \hat{j}=\hat{k} $
Therefore $ E _{x}\hat{i}\times B _{y}\hat{j}=C\hat{k} $ i.e. E is along x-axis and B is along y-axis.
