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consider an electromagnetic wave traveling in vacuum. Recall that the speed of l

ID: 1377490 • Letter: C

Question

consider an electromagnetic wave traveling in vacuum. Recall that the speed of light in vacuum is c = 3 x 10^8 m/s. The electric field corresponding to this wave is given by: Vector E = (10 V/m) cos(ky + 2 pi . 10^12 s^-1 . t) hat i + (10 V/m) cos(ky + 2 pi . 10^12s^-1 . t) hat k (1) Here hat I, hat j and hat k are perpendicular unit vectors associated with the cartesian coordinates x. y, and z respectively. (a) What is the direction of propagation of this wave? (b) What is the frequency f in Hertz and the wavelength A in meters?

Explanation / Answer

(A) here electric field is in Y- direction, so magnetic field will be in Z- direction ( perpendicular to electric field) .

So the direction of propagation of electromagnetic wave will be in X- direction.

( B ) If we compare the electric field with standard equatiion:

E = E0 cos ( Ky + 2*pie*f*t ) i^ + E0 cos ( ky+ 2*pie*f*t ) k^

frequency f = 1012 Hz

wavelength ( lambda) = c / frequency

= 3*108 / 1012 = 3*10-4 m