- #1

- 602

- 0

**Confused on Constructive/Destructive Interference!!!**

## Homework Statement

A film with n=1.6 is deposited on glass. What is the thinnest film that will produce constructive interference in the reflection of light with a wavelength of 575 nm?

## Homework Equations

## The Attempt at a Solution

I have 2 equations that I can choose from...

Constructive Interference for 0 to 2 refl. phase changes

Destructive Interference for 1 refl. phase changes

2T = m * t/n

t = wavelength

Destructive Interference for 0 to 2 refl. phase changes

Constructive Interference for 1 refl. phase changes

2T = (m + 1/2) * t/n

t = wavelength

How do I know which one to use?

I chose the 2nd one because I assumed there was only 1 phase change.

How do figure out what m =???