A fish, looking up through the water sees the outside world contained in a circular horizon. If the refractive index of water is 4 3 and the fish is 12 cm below the surface of the water, the radius of the circle in centimetre is

From figure, tan ⁡ C = r 12 o r r = 12 tan ⁡ C o r r = 12 sin ⁡ C 1 - sin 2 ⁡ C r = 12 × 1 μ 1 - 1 μ 2 = 12 μ 2 - 1 = 12 4 3 2 - 1 i . e . , r = 12 × 3 7 = 36 7

Physics - Geometrical Optics Question with Solution | TestHub

PhysicsGeometrical OpticsRefraction at plane surfaceEasy2 minPYQ_2020

PhysicsEasysingle choice

A fish, looking up through the water sees the outside world contained in a circular horizon. If the refractive index of water is $\frac{4}{3}$ and the fish is $12 cm$ below the surface of the water, the radius of the circle in centimetre is

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Solution:

From figure, $\tan C = \frac{r}{12}$

$o r r = 12 \tan C$

$o r r = \frac{12 \sin C}{\sqrt{1 - \sin^{2} C}}$

$r = \frac{12 \times \frac{1}{μ}}{\sqrt{1 - \frac{1}{μ^{2}}}} = \frac{12}{\sqrt{μ^{2} - 1}} = \frac{12}{\sqrt{{(\frac{4}{3})}^{2} - 1}}$

$i . e ., r = \frac{12 \times 3}{\sqrt{7}} = \frac{36}{\sqrt{7}}$

Stream:NTA_ABHYAS_NEETSubject:PhysicsTopic:Geometrical OpticsSubtopic:Refraction at plane surface

⏱ 2mℹ️ Source: PYQ_2020

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