Question:

Consider a configuration of $n$ identical units, each consisting of three layers The first layer is a column of air of height $h=\frac{1}{3} cm$, and the second and third layers are of equal thickness $d=\frac{\sqrt{3}-1}{2} cm$, and refractive indices $\mu_1=\sqrt{\frac{3}{2}}$ and $\mu_2=\sqrt{3}$, respectively. A light source $O$ is placed on the top of the first unit, as shown in the figure. A ray of light from $O$ is incident on the second layer of the first unit at an angle of $\theta=60^{\circ}$ to the normal. For a specific value of $n$, the ray of light emerges from the bottom of the configuration at a distance $l=\frac{8}{\sqrt{3}} cm$, as shown in the figure The value of $n$ is ______
dentical units, each consisting of three layers

Updated On: Apr 23, 2024
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Correct Answer: 4

Solution and Explanation

The value of n is 4.

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Concepts Used:

Moment of Inertia

Moment of inertia is defined as the quantity expressed by the body resisting angular acceleration which is the sum of the product of the mass of every particle with its square of a distance from the axis of rotation.

Moment of inertia mainly depends on the following three factors:

  1. The density of the material
  2. Shape and size of the body
  3. Axis of rotation

Formula:

In general form, the moment of inertia can be expressed as, 

I = m × r²

Where, 

I = Moment of inertia. 

m = sum of the product of the mass. 

r = distance from the axis of the rotation. 

M¹ L² T° is the dimensional formula of the moment of inertia. 

The equation for moment of inertia is given by,

I = I = ∑mi ri²

Methods to calculate Moment of Inertia:

To calculate the moment of inertia, we use two important theorems-

  • Perpendicular axis theorem
  • Parallel axis theorem