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PhysicsGeometrical OpticsRefraction at plane surfaceHard2 minPYQ_2022
PhysicsHardnumerical

Consider a configuration of n identical units, each consisting of three layers. The first layer is a column of air of height h=13 cm, and the second and third layers are of equal thickness d=3-12 cm, and refractive indices μ1=32 and μ2=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 θ=60° to the normal. For a specific value of n, the ray of light emerges from the bottom of the configuration at a distance l=83 cm, as shown in the figure. The value of n is _______.

Question diagram: Consider a configuration of n identical units, each consisti
Answer:
4.00
Solution:

Considering a single unit with three layers. The figure below shows the refraction of light as it moves from one medium to others.

For the first interface, 

x1=13×tan60°=13 cm

Using Snell's law,

μ1sinθ1=μ2sinθ2

1×32=32×sinθ2

θ2=45°

For the second interface,

x2=d×tan45°=d

And again using Snell's law,

32×sin45=3×sinθ3

32×12=3sinθ3

θ3=30°

x3=d×tan30°=d3

 x1+x2+x3=13+3-121+13

=23 cm

 n=1x1+x2+x3=8323=4

Thus, the value of n=4.

Stream:JEE_ADVSubject:PhysicsTopic:Geometrical OpticsSubtopic:Refraction at plane surface
2mℹ️ Source: PYQ_2022

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