CBSE 2026 · Region 5 · Set 1 · Q6 · 1 mark
The magnetic field in a plane electromagnetic wave travelling in glass $\displaystyle (\mathrm{n}=1 \cdot 5)$ is given by \[\mathrm{B}_{\mathrm{y}}=\left(2 \times 10^{-7} \mathrm{~T}\right) \sin \left(\alpha \mathrm{x}+1 \cdot 5 \times 10^{11} \mathrm{t}\right) \] where x is in metres and t is in seconds. The value of $\displaystyle \alpha$ is :
Official answer
From CBSE’s own marking scheme for this paper.
(C)
$\displaystyle 7.5 \times 10^{2} \mathrm{~m}^{-1}$
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CBSE Class 12 Physics past-paper question from the 2026board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.