A linearly polarised electromagnetic wave given as `E=E_(0)haticos(kz-omegat)` is incident normally on a perfectly reflecting wall `z=a`. Assuming that the material of the optically inactive, the reflected wave will be give as

Options

A. `E_(r) =E_(0) hati (kz - omegat)`
B. `E_(r)=E_(0) hati "cos" (kz +omegat)`
C. `E_(r) =- E_(0) hati " cos " (kz +omegat)`
D. `E_(r) =E_(0) hati " sin "(kz - omegat)`

Answer

B

Explanation

When a wave is reflected from denser medium then e. type of wave doesn't change but only its phase changes by `180^(@) " or " pi` radian.
thus for the reflected wave `hatz =- hatz hati =- hati` and additional phase of `pi` in the incident wave.
Given. here the incident electromagnetic wave is ,
`E=E_(0) hati " cos " (kz -omegat)`
The reflected electromagnetic wave is given by
`E_(r) =E_(0) (-hati) " cos "[K(-z) - omegat +pi]`
`=- E_(0) hati " cos "[-(kz + omegat) +pi]`
`=E_(0) hati "cos "[-kz + omegat) + pi]`
`=E_(0) hati " cos "[-(k_(z) +omegat)=E_(0) hati " cos "(kz + omegat)]`