Question

UIT VV Iru СПС врете. . Electric field associated with Electro-magnetic wave is Ē= E, sin (kz) sin (wt)i, Cal- culate average value of Poynting vector? Why can't we use the relations Ē = -(Ex)and B = (KXE) for the case of standing waves and spherical waves? For the given standing wave Ē = E, sin (kz) sin (wt) i find the value of B.​

Answer 1

Answer:

12th>Physics>Electromagnetic Waves>Nature and Characteristics of Electromagnetic Waves>The electric field associat...

Physics

The electric field associated with an electromagnetic wave in vacuum is given by ∣E∣=40 cos(kz−6×108t), where E, z and t are in volt per meter, meter and second respectively. The value of wave vector k is:

A

2 m−1

B

0.5 m−1

C

3 m−1

D

6 m−1

Medium

Share

Answer

Open in answr app

Correct option is

A

2 m−1

Given: The electric field associated with  an electromagnetic wave in vacuum is given by ∣E∣=40cos(kz−6×108t)

To find: Value of wave vector k

Solution: 

We know electromagnetic wave eqution is

∣E∣=E0cos(kz−ωt)

And given equation is

∣E∣=40cos(kz−6×108t)

By comparing these two, we get

ω=6×108 and 

E0=40

We also know,

Speed of electromagnetic wave is given by:

v=kω

where v is the speed of the light.

Hence, 

k=vω

Answer 2

Answer:

Average energy density of electromagnetic wave

Uav=

1

2

 

ε0E

2

0

=

1

2

 

×(8.85×10-12)×(502)

10-8j/m3