Verified Solution • 2025–26 Session moderate

QJEEM25Phc6eb: JEE Main 2025 Physics - Class 12 JEEM25Phc6eb 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 nm . [Assume that the light is incident nearly perpendicular to the glass surface.]

Multiple Choice Options

  • A 68.7 nm
  • B 137.5 nm
  • C 94.8 nm
  • D 275 nm

Step-by-Step Verified Solution

JEE Main 2025 (Online) 22nd January Evening Shift Physics - Wave Optics Question 6 English Explanation

For transmitted green light to be maxima, reflected green should be minima.

amp;ΔP=2μ0t=nλamp;⇒t=nλ2μ0∴tmin⁡=λ2μ0=5502×2=137.5\begin{aligned}& \Delta \mathrm{P}=2 \mu_0 \mathrm{t}=\mathrm{n} \lambda \\& \Rightarrow \mathrm{t}=\frac{\mathrm{n} \lambda}{2 \mu_0} \therefore \mathrm{t}_{\min }=\frac{\lambda}{2 \mu_0}=\frac{550}{2 \times 2}=137.5\end{aligned}

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