JEE Main 2026 · 2 Apr · Shift 1 · Physics Q43

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An electromagnetic wave travelling in $x$ -direction is described by field equation $E_y=300\sin\omega\left(t-\dfrac xc\right)$ . If the electron is restricted to move in $y$ -direction only with speed of $1.5\times10^6$ m/s then ratio of maximum electric and magnetic forces acting on the electron is ________.

200

150

400

300

Answer and worked solution

Official answer: A

Forces. $F_E=eE_0$ . In an EM wave $B_0=\frac{E_0}c$ , and the magnetic force is $F_B=evB_0=\frac{evE_0}c$ .

Ratio. $\dfrac{F_E}{F_B}=\dfrac cv=\dfrac{3\times10^8}{1.5\times10^6}=200$ .

(A)

Topics:Properties of EM waves Force on a moving charge

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JEE Main 2026 · 2 Apr · Shift 1, Physics question 43