Geometrical problem related to thin film interference

AI Thread Summary
The discussion focuses on proving the optical path length difference in thin film interference, specifically the equation Δ=n(BC+CD)-BE=2nd cos(r). The poster is struggling to derive the term 2nd cos(r) and has attempted trigonometric methods without success. They clarify that this inquiry is independent of their coursework and is aimed at understanding the concept of thin film interference under non-perpendicular incidence. Visual aids are provided to assist in the explanation. The thread highlights the challenges of applying trigonometry to this optical problem.
khaos89
Messages
8
Reaction score
0
Look at the picture below, I have to prove that the optical path length difference is

\Delta=n(BC+CD)-BE=2nd\cos(r)

[PLAIN]http://img200.imageshack.us/img200/2271/schermata082455775alle1.th.png

The problem is just how to get 2nd\cos(r)

I actually don't have any idea :\

I have tried to work with trigonometry but no luck yet...

(I am posting it here because it's not related to course work, i am just trying to understand how it works when we don't have perpendicular incidence)
 
Last edited by a moderator:
Mathematics news on Phys.org
Sorry, here we go with the pic:

[PLAIN]http://img193.imageshack.us/img193/2271/schermata082455775alle1.png
 
Last edited by a moderator:
Thanks a lot :)
 
Thread 'Video on imaginary numbers and some queries'

Thread 'Video on imaginary numbers and some queries'

Hi, I was watching the following video. I found some points confusing. Could you please help me to understand the gaps? Thanks, in advance! Question 1: Around 4:22, the video says the following. So for those mathematicians, negative numbers didn't exist. You could subtract, that is find the difference between two positive quantities, but you couldn't have a negative answer or negative coefficients. Mathematicians were so averse to negative numbers that there was no single quadratic...
View full post »

Thread 'What Exactly is Dirac’s Delta Function? - Insight'

Insights auto threads is broken atm, so I'm manually creating these for new Insight articles. In Dirac’s Principles of Quantum Mechanics published in 1930 he introduced a “convenient notation” he referred to as a “delta function” which he treated as a continuum analog to the discrete Kronecker delta. The Kronecker delta is simply the indexed components of the identity operator in matrix algebra Source: https://www.physicsforums.com/insights/what-exactly-is-diracs-delta-function/ by...
View full post »

Thread 'Non-orthogonal bases'

Suppose ,instead of the usual x,y coordinate system with an I basis vector along the x -axis and a corresponding j basis vector along the y-axis we instead have a different pair of basis vectors ,call them e and f along their respective axes. I have seen that this is an important subject in maths My question is what physical applications does such a model apply to? I am asking here because I have devoted quite a lot of time in the past to understanding convectors and the dual...
View full post »

Similar threads

Effect on visibility of thin films due to interference
Replies
35
Views
3K
A Structural coloration of a zeolite monolayer
Replies
7
Views
2K
Interference in thin films; confusion regarding geometry
Replies
4
Views
1K
A problem involving thin film interference
Replies
2
Views
2K
How to know what m value to plug into thin film interference equations
Replies
3
Views
12K
How to Calculate Radius of Curvature from Thin Film Interference?
Replies
2
Views
2K
Thin film interference - why thin, exactly?
Replies
8
Views
3K
Thin film interference and external / internal reflection
Replies
1
Views
2K
How Does Thin Film Interference Affect Light Reflection?
Replies
1
Views
2K
Thin film constructive interference
Replies
3
Views
4K

Hot Threads

Recent Insights

Back
Top