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**1. Homework Statement**

Monochromatic light, at normal incidence, strikes a thin film in air. If λ denotes the wavelength in the film, what is the thinnest film in which the reflected light will be a maximum?

A

λ/4

B

3λ/4

C

λ

D

much less than λ

E

λ/2

**2. Homework Equations**

n air ∠ n glass

so at the first reflection it will cuase a 180° ray out of phase while the second ray refected from the inside it will stay inphase because n air ∠ n glass

so for constructive interference: 2L=odd number*λ/2

**3. The Attempt at a Solution**

least odd number is one , so L=λ/4 ?? why it is incorrect

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