$+x$ દિશામાં ગતિ કરતાં વિદ્યુતચુંબકીય તરંગ માટે આવૃતિ $2 \times 10^{14}\,Hz$ અને વિદ્યુતક્ષેત્રનું મૂલ્ય $27\,Vm^{-1}$ છે. આ તરંગ માટે આપેલ ચાર વિકલ્પ પૈકી કોણ ચુંબકીયક્ષેત્રને સાચી રીતે દર્શાવે છે?

Question

A$\vec B\,(x\,,\,t) = (3 \times {10^{ - 8}}\,T)\,\hat j \;\sin \,[2\pi \,(1.5 \times {10^{ - 8}}\,x\, - \,2 \times {10^{14}}\,t)]$
B$\vec B\,(x\,,\,t) = (9 \times {10^{ - 8}}\,T)\,\hat i\; \sin \,[2\pi \,(1.5 \times {10^{ - 8}}\,x\, - \,2 \times {10^{14}}\,t)]$
C$\vec B\,(x\,,\,t) = (9 \times {10^{ - 8}}\,T)\,\hat j\;\sin \,[(1.5 \times {10^{ - 6}}\,x\, - \,2 \times {10^{14}}\,t)]$
D$\vec B\,(x\,,\,t) = (9 \times {10^{ - 8}}\,T)\,\hat k \;\sin \,[2\pi \,(1.5 \times {10^{ - 6}}\,x\, - \,2 \times {10^{14}}\,t)]$

JEE MAIN 2015, Medium

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Solution

d
As we know,

$B_{0}=\frac{E_{0}}{C}=\frac{27}{3 \times 10^{8}}=9 \times 10^{-8}$ $tesla$

Oscillation of $B$ can be only along $\hat{\jmath}$ or $\hat{k}$ direction.

$\omega=2 \pi f=2 \pi \times 2 \times 10^{14} \,\mathrm{Hz}$

$\therefore \bar{B}(x, t)=\left(9 \times 10^{-8} T\right) \hat{k} \sin [2 \pi(1)\left.1.5 \times 10^{-6} \times-2 \times 10^{4} t\right)$

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