GATE EC 2023 Set 1 — Question 60
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Electromagnetics → Plane Waves → Reflection & Refraction
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Question
A transparent dielectric coating is applied to glass () to eliminate the reflection of red light (). The minimum thickness of the dielectric coating, in , that can be used is _________ (rounded off to two decimal places).
Correct answer
0.12 to 0.14
Solution
To eliminate reflection at the interface between air () and glass (), an anti-reflection coating is used.
1.Refractive index of the coating ():
For zero reflection, the characteristic impedance (or refractive index) of the coating should be the geometric mean of the surrounding media:2.Minimum thickness ():
The minimum thickness for destructive interference (zero reflection) is a quarter-wavelength in the coating material:Given :Rounding to two decimal places, the minimum thickness is .Continue learning with Success Tracker
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