Instrumentation Engineering
2018 · Paper 1
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Complete GATE IN 2018 Paper 1 overview, original pages and practice · Timed previous-paper practice
Questions 64–65 of 65. Imported answers require review unless explicitly marked reviewed.
Question 54
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A Michelson Interferometer using a laser source of wavelength λ₀ = 500 nm, with both the mirrors (M₁ & M₂) fixed and positioned equidistant from the splitter/combiner is shown in the figure. When a dielectric plate of refractive index n = 1.5, of thickness t, is placed in front of the mirror M₂, a dark fringe is observed on the detector. If the dielectric plate is removed without changing the position of the mirrors M₁ & M₂, a bright fringe is observed on the detector. The minimum thickness t (in nm) of the dielectric is _______.
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A multi-mode optical fiber with a large core diameter has a core refractive index n₁ = 1.5 and cladding refractive index n₂ = 1.4142. The maximum value of θₐ (in degrees) for which the incident light from air will be guided in the optical fiber is ±_____.
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