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Ray Optics — JEE physics STD 12 Science — Question

CBSE BoardEnglish MediumSTD 12 ScienceJEE physicsRay Optics1 Mark
MCQ
If the critical angle for total internal reflection from a medium to vacuum is $30^{\circ}$, the velocity of light in the medium is
  • A
    $3 \times 10^8 \mathrm{~m} / \mathrm{s}$
  • ✓
    $1.5 \times 10^8 \mathrm{~m} / \mathrm{s}$
  • C
    $6 \times 10^8 \mathrm{~m} / \mathrm{s}$
  • D
    $\sqrt{3} \times 10^8 \mathrm{~m} / \mathrm{s}$
✓

Answer

Correct option: B.
$1.5 \times 10^8 \mathrm{~m} / \mathrm{s}$
$ \mu=\frac{1}{\sin C}=\frac{1}{\sin 30}=2 $
$ \therefore v=\frac{3 \times 10^8}{2}=1.5 \times 10^8 \mathrm{~m} / \mathrm{s}$

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