NEET UG 2022 — Physics Optics

2022mcqhard

Two transparent media $A$ and $B$ are separated by a plane boundary. The speed of light in those media are $1.5\times {10}^{8}m{s}^{-1}$ and $2.0\times {10}^{8}m{s}^{-1}$ , respectively. The critical angle for a ray of light for these two media is:

Official previous-year question

Held on 30 Apr 2022 · Verified 9 Jul 2026.

Options

A
${\mathrm{sin}}^{-1}(0.750)$
B
${\mathrm{tan}}^{-1}(0.500)$
C
${\mathrm{tan}}^{-1}(0.750)$
D
${\mathrm{sin}}^{-1}(0.500)$

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Solution

Refractive index $(\mu )$ in terms of speed of light $(c)$ in vacuum and wave speed $(v)$ in medium is given by, $\mu =\frac{c}{v}$ .

So, for medium $A$ , ${\mu }_{A}=\frac{c}{{v}_{A}}=\frac{3\times {10}^{8}}{1.5\times {10}^{8}}=2$ and for medium $B$ , ${\mu }_{B}=\frac{c}{{v}_{B}}=\frac{3\times {10}^{8}}{2\times {10}^{8}}=1.5$

For critical angle, angle of refraction $r=90^{\circ}$ .

Using Snell's law,

${\mu }_{1}\mathrm{sin}i={\mu }_{2}\mathrm{sin}r$

$\Rightarrow 2\mathrm{sin}i=1.5\mathrm{sin}90^{\circ} \Rightarrow \mathrm{sin}i=\frac{1.5}{2}=0.750 \Rightarrow i={\mathrm{sin}}^{-1}(0.750)$

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Solution

Refractive index $(\mu )$ in terms of speed of light $(c)$ in vacuum and wave speed $(v)$ in medium is given by, $\mu =\frac{c}{v}$ .

So, for medium $A$ , ${\mu }_{A}=\frac{c}{{v}_{A}}=\frac{3\times {10}^{8}}{1.5\times {10}^{8}}=2$ and for medium $B$ , ${\mu }_{B}=\frac{c}{{v}_{B}}=\frac{3\times {10}^{8}}{2\times {10}^{8}}=1.5$

For critical angle, angle of refraction $r=90^{\circ}$ .

Using Snell's law,

${\mu }_{1}\mathrm{sin}i={\mu }_{2}\mathrm{sin}r$

$\Rightarrow 2\mathrm{sin}i=1.5\mathrm{sin}90^{\circ} \Rightarrow \mathrm{sin}i=\frac{1.5}{2}=0.750 \Rightarrow i={\mathrm{sin}}^{-1}(0.750)$

NEET UG 2022 — Physics Optics

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NEET UG 2022 — Physics Optics

Options

Did you get this right?

Solution

Your note

NEET UG Optics in other years

More NEET UG Optics questions

Other Physics topics for NEET UG

Mechanics

Electromagnetism

Modern Physics

Thermodynamics

Waves & Oscillations

Keep practicing Optics