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STD 12 - 9. Ray optics abd optical instruments — JEE STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceJEESTD 12 - 9. Ray optics abd optical instruments4 Marks
MCQ
When the rectangular metal tank is filled to the top with an unknown liquid, as observer with eyes level with the top of the tank can just see the corner $E$; a ray that refracts towards the observer at the top surface of the liquid is shown. The refractive index of the liquid will be
  • ✓
    $1.2$
  • B
    $1.4$
  • C
    $1.6$
  • D
    $1.9$
✓

Answer

Correct option: A.
$1.2$
a
(a) Light ray is going from liquid $(Denser)$ to air $(Rarer)$ and angle of refraction is ${90^o}$, so angle of incidence must be equal to critical angle
from figure
$\sin C = \frac{4}{5}$
Also $\mu = \frac{1}{{\sin C}} = \frac{5}{4} = 1.2$

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