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Most Important Selected Qs for JEE AdvancedPhysicsRay Optics

Plane wave fronts are incident are incident on a glass slab which has refractive index as a function of distance Z , according to the relation = ₀ (1- Z^2 Z₀^2 ) , where ₀ is the refractive index along the axis and Z₀ is a constant. This glass slab can act as lens of focal length F(Z F) . (Incident rays are normal to the slab)

Options

  1. AZ₀^2 (2 ₀ t )
  2. BZ₀^2 ( ₀ t )
  3. C₀ Z₀^2 (2 t)
  4. DNone

Correct answer

A. Z₀^2 (2 ₀ t )

Step-by-step solution

Since the rays focus at same time, hence optical path length for all rays must be same. gathered z^2+F^2 + ₀ [1- z^2 z₀^2 ] t=F+ ₀ t F [1+ z^2 2 F ]=F+ ₀ z^2 z₀^2 t F= z₀^2 2 t gathered

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