Verified Solution • 2025–26 Session moderate

QJEEMP_2025_9: JEE Main 2025 Physics - Class 12 JEEMP_2025_9 Solution: A transparent film of refractive index, 2.0 is coated on a…

A transparent film of refractive index, 2.0 is coated on a glass slab of refractive index, 1.45. What is the minimum thickness of transparent film to be coated for the maximum transmission of Green light of wavelength 550 nm550\text{ nm} . [Assume that the light is incident nearly perpendicular to the glass surface.]

Multiple Choice Options

  • A 68.7 nm7\text{ nm}
  • B 137.5 nm5\text{ nm}
  • C 94.8 nm8\text{ nm}
  • D 275 nm275\text{ nm}

Step-by-Step Verified Solution

For transmitted green light to be maxima, reflected green should be minima. Δ P = 2 μ 0 t = n λ ⇒ t = n λ 2 μ 0 ∴ t min = λ 2 μ 0 = 550 2 × 2 = 137.5

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