Question

JEE MAINS PHYSICS QUESTION SEPTEMBER 2020

Answer 1

Electric field in Electromagnetic waves is E = E₀(i + j)sin(kz - ωt)

we have to find the equation of magnetic field.

solution : let peak value of magnetic field is B₀.

well, you can find peak value of it using formula,

B₀C = E₀, here C is speed of light.

we know, in electromagnetic waves, electric field is perpendicular on magnetic field.

i.e., E.B = 0

here, if we take B = B₀(-i + j) sin(kz - ωt)

then, E.B = E₀B₀sin²(kz -ωt) [(i + j) .( -i + j) ]

= E₀B₀sin²(kz -ωt) [ - 1 + 1 ]

= 0

so equation of magnetic field is B = B₀(-i + j) sin(kz - ωt)

Therefore option (1) is correct choice.