An electromagnetic wave from a wire antenna travels from the

An electromagnetic wave from a wire antenna travels (from the reader) toward the plane of the paper. At time t = 0.0 s it strikes the paper at normal incidence. At point O and t = 0.0 s, the magnetic field vector has its maximum value, 3.10×10^-8 T, pointing in the negative y-direction. The frequency of this wave is 2.61×10⁶ Hz.

a) What is the x-component of the associated electric field E at time t = 0.0 s? (Use the right-hand rule to determine the direction of E, and hence the sign of the x-component.)

b) What is the magnitude of the Poynting vector of the wave at time t = 0.0 s?

c) What is the y component of the magnetic field at point O at time 1.92×10^-7 s?

Solution

A) speed of wave = 3 x 10^8 m/s

and v B = E

E = 3 x 10^8 x 3.1x 10^-8 = 9.3 N/C .....ANs

B) s(t) = (E x B) / u0

= (9.3 x 3.1 x 10^-8) / (4 x pi x 10^-7) = 0.2294

direction = inside the papaer

C) time period , T = 1/f = 1 / (2.61x 10^6) = 3.831 x 10^-7 s

at half the time period, magnitude will be same at t= 0 but in opposite direction,

B = 3.10×10-8 T T pointing in positive y direction.