Physics - Geometrical Optics Question with Solution | TestHub

PhysicsGeometrical OpticsRefraction at plane surfaceEasy2 minPYQ_2020

PhysicsEasysingle choice

A ball is dropped from a height of $20 m$ above the surface of the water in a lake. The refractive index of water is $\frac{4}{3}$ . A fish inside the lake, in the line of fall of ball is looking at the ball. At an instant, when the ball is $12.8 m$ above the water surface, the fish sees speed of ball as

Options:

Answer:

Solution:

$υ = \sqrt{2 gh} = \sqrt{2 \times 10 \times 7}$

$= 12 {ms}^{-1}$

In this case when eye is inside water,

$x_{app.} = μ x$

$∴ \frac{d x_{app.}}{dt} = μ \cdot \frac{d x}{dt}$

or, $υ_{app.} μ υ = \frac{4}{3} \times 12 = 16 {m s}^{-1}$

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

⏱ 2mℹ️ Source: PYQ_2020

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