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Thin film thickness for maximum or minimum transmission

This type of question, asked 2 times: 22 Jan 2025, 28 Jan 2025. All 2 questions below, oldest first.

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  1. Question 1

    22 Jan 2025

    92
    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.]

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  2. Question 2

    28 Jan 2025

    100
    A thin transparent film with refractive index 1.4, is held on circular ring of radius 1.8 cm . The fluid in the film evaporates such that transmission through the film at wavelength 560 nm goes to a minimum every 12 seconds. Assuming that the film is flat on its two sides, the rate of evaporation is _____\_\_\_\_\_ π×10−13 m3/s\pi \times10^{- 13}{\text{ }m}^{3}/s.