Q153 / 160 · TS EAMCET 2022 (19 Jul Shift 2) · Physics

A laser beam has intensity $2.1 \times 10^{15} \mathrm{~W} / \mathrm{m}^2$. The amplitude of magnetic field in the beam in approximately is

  • A
    1.4 T
  • Correct answer
    B
    4.2 T
  • C
    1 T
  • D
    1.5 T

Solution

$\mathrm{I}=\frac{\mathrm{B}_0^2}{2 \mu_0} \mathrm{C}$ $\begin{aligned} & \Rightarrow \quad 2.1 \times 10^{15}=\frac{\mathrm{B}_0^2 \times 3 \times 10^8}{8 \pi \times 10^{-7}} \\ & \Rightarrow \quad \mathrm{B}_0^2=17.64 \\ & \Rightarrow \quad \mathrm{B}_0=4.2 \mathrm{~T}\end{aligned}$

Hence, the correct answer is option: 'B'.

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