Q7 / 116 · NTA Abhyas (JEE Main) 2020 · Physics · Ray Optics

A rectangular tank filled with some liquid is accelerated along a horizontal surface at 403 m s-2. Inside the liquid, a laser pointer is fixed a the centre of the tank which shoots a thin laser beam in the vertically upward direction. If after refraction from the liquid surface, the laser beam moves along the surface of the liquid, then what is the refractive index of the liquid?

Correct answer: 1.25

Solution

Figure

Figure
Due to the pseudo force, the free surface of the liquid will become inclined. If θ is the angle made by the free surface of the liquid with the horizontal, then

tanθ=ag=43

⇒sinθ=45

Using snell's law we get

μ sinθ=1

μ=1sinθ=54=1.25

Hence, the correct answer is 1.25.

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