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Vidushi Saklani posted an Question
September 27, 2021 • 01:03 am
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30 points
30 points
- IIT JAM
- Physics (PH)
According to me wave is travelling in x direction e=ej and for b=bk so when we calculate magnetic field vector it should be j×k =i cap but its zcap..plz explain
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Isha lohan 1 Best Answer
You can clearly eliminate option A and D as in A the cos term should be (kx-wt) and in D none of the E or B can be in xcap direction. Now, The rule is - To find the direction of propagation of an E&M wave, point the fingers of the right hand in the direction of the electric field, curl them toward the direction of the magnetic field, and your thumb will point in the direction of propagation. Now, coming to your ques, the propagation direction is x, so point your thumb in x direction, and point your fingers in y cap direction and curl them, they will curl towards z direction. So, E is ycap And B is zcap. Therfore option B correct. May be your confusion in the given solution is due to the kcap cross E vector term in second line, note that here k is not the unit vector i, j, k. Rather this k is the wave number k, which have direction of propagation, i.e.,xcap. So, k cross E means, xcap cross ycap, which gives B in zcap direction Ask if still any doubt. .