Question

An EM wave propagating in x-direction has a wavelength of 8 mm. The electric field vibrating y-direction has maximum magnitude of 60 Vm-1. Choose the correct equations for electric and magnetic field if the EM wave is propagating in vacuum:

• A. $Ey=60sin⁡[\frac{π}{4}×10^3(x−3×10^8t)]\hat{j}Vm^{−1}$
  $Bz=2sin⁡[\frac{π}{4}×10^3(x−3×10^8t)]\hat{k}T$
• B. $Ey=60sin⁡[\frac{π}{4}×10^3(x−3×10^8t)]\hat{j}Vm^{−1}$
  $Bz=2× 10^{-7} sin⁡[\frac{π}{4}×10^3(x−3×10^8t)]\hat{k}T$
• C. $Ey=2× 10^{-7}sin⁡[\frac{π}{4}×10^3(x−3×10^8t)]\hat{j}Vm^{−1}$
  $Bz=60 sin⁡[\frac{π}{4}×10^3(x−3×10^8t)]\hat{k}T$
• D. $Ey=2× 10^{-7}sin⁡[\frac{π}{4}×10^4(x−4×10^8t)]\hat{j}Vm^{−1}$
  $Bz=60 sin⁡[\frac{π}{4}×10^4(x−4×10^8t)]\hat{k}T$

Answer 1

Answer: (B)

$Ey=60sin⁡[\frac{π}{4}×10^3(x−3×10^8t)]\hat{j}Vm^{−1}$
$Bz=2× 10^{-7} sin⁡[\frac{π}{4}×10^3(x−3×10^8t)]\hat{k}T$

Answer 2

In first 3 options speed of light is 3 × 108 m/sec and in the fourth option it is 4 × 108 m/sec.
Using E = CB
We can check the option is B.