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 inc

Question

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.] [2025]

Smart Achievers · Accepted Answer

(3)

For maximum transmission, reflection is zero.

$∴$ For green light there should be minima for interference of two reflected lights.

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

$△ x = 2 μ_{0} t = n λ$

$\Rightarrow t = \frac{n λ}{2 μ_{0}}$

$∴ t_{\min} = \frac{λ}{2 μ_{0}} = \frac{550}{2 \times 2} = 137.5 nm$

Solution

1 94.8 nm

2 68.7 nm

3 137.5 nm

4 275 nm

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