JEE Main · 2021 · 25 Jul 2021 · Shift 1 · EM Waves

Comparing with $E_0\cos (kz-\omega t)$ gives $k=1.8$ rad/m and $\omega =5.4\times 10^6$ rad/s, so the wavelength is $\lambda =\frac{2\pi }{k}=3.5$ m and the frequency is $f=\frac{\omega }{2\pi }=8.6\times 10^5$ Hz. A perfectly reflecting wall transmits nothing, so the whole wave returns along the $-z$ direction with the same amplitude, wave number and angular frequency, and reversing the direction of travel reverses the sign of the $z$ term relative to the $t$ term in the phase. The reflected wave is $3.1\cos \left[(1.8)z+\left(5.4\times 10^6\right)t\right]\hat{i}$ N/C.