How Do You Derive the Constructive Interference Equation for Reflection?

[baileya]

Homework Statement

Derive the equation 2t=(n+1/2)(lamba/index of refraction) to show it's the correct eq'n for constructive interference on reflection. Include a diagram.

Homework Equations

2t=(n+1/2)(lambda/index of refraction)

The Attempt at a Solution

I'm not sure how you'd show it's the correct eq'n...

 

[tiny-tim]

hi baileya!

(have a lambda: λ )

… Include a diagram.
…
I'm not sure how you'd show it's the correct eq'n...

you'd draw a diagram!

what does it show? ​