Electric and Magnetic fields oscillate sinusoidally in an Electromagnetic Waves. The oscillating electric field cannot be represented in this way, where the symbols have their usual meaning:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → $E=E_0 \sin \left[\frac{2 \pi}{T}(v z-t)\right]$
(A) $E=E_0 \sin (k z-\omega t)$ General form.
(B) $E=E_0 \sin \left[\frac{2 \pi z}{\lambda}-\frac{2 \pi}{T} t\right]$
$=E_0 \sin [k z-\omega t]~~~~~\left[∵ k=\frac{2 \pi}{\lambda}, \omega=\frac{2 \pi}{T}\right]$
(C) $E=E_0 \sin \left[\frac{2 \pi}{\lambda} z-\frac{2 \pi v}{\lambda} t\right]$
$=E_0 \sin [k z-2 \pi v t] ~~~~~\left[\text { frequency } v=\frac{v}{\lambda}\right]$
$=E_0 \sin [k z-\omega t]$
(D) Dimensionally incorrect