Optical Path Difference for Thin - Film Interference (Normal Incidence)
Formula: Δ L = 2n₂d + (λ)/(2), where Δ L is the optical path difference, n₂ is the refractive index of the film, d is the film thickness, and λ is the waveleng…
Syllabus path: Optics › Physical Optics › Interference
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CSCA Physics Formula Reference
Formula and explanation
Formula: Δ L = 2n₂d + (λ)/(2), where Δ L is the optical path difference, n₂ is the refractive index of the film, d is the film thickness, and λ is the wavelength in vacuum. The additional λ/2 term arises from the half - wave loss upon reflection from a medium of lower refractive index to a higher one. Conditions: Light is incident normally (or approximately normally) on the film surface. Explanation: This formula is often used to calculate the thickness of anti - reflection or high - reflection coatings.
Related tutorial and examples
Interference
Topic: Optics > Physical Optics > Interference Interference 1. Conceptual Definition Interference is the core of wave optics, referring to the phenomenon where two or more coherent waves superimpose in space to form stable patterns of bright and dark fringes. Key Exam Point: Cohe…
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