<< Chapter < Page
  Waves and optics   Page 1 / 1
Chapter >> Page >
We show how the evanescent wave arises.

We saw that when the index of refraction of the incident material is greater than the transmitting material we can get total internal reflection at thecritical angle. An interesting question is "what happens at larger angles of incidence?" This actually is somewhat subtle. From simple trigonometry we knowthat cos θ t = 1 sin 2 θ t . We also know from Snell's law that sin θ t = n i n t sin θ i so we have cos θ t = 1 n i 2 n t 2 sin 2 θ i . So we see that if n i > n t cos θ t can become an imaginary number! For convenience we will write this as cos θ t = i n i 2 n t 2 sin 2 θ i 1 Now lets write down the expression for the transmitted wave: E t = E 0 t e i ( K t r ω t ) For simplicity we will assume that the interface lies in the y = 0 plane and thus the y direction is normal to the interface. Also, we assume the z = 0 plane defines then plane of incidence. Then we can write K t = ( K t x , K t y , 0 ) or K t = ( K t sin θ t , K t cos θ t , 0 ) . Also r = ( x , y , 0 ) .

So now we can write that the wave as E t = E 0 t e i ( K t r ω t ) E t = E 0 t e i K t sin θ t x e i K t cos θ t y e i ω t or E t = E 0 t e i K t sin θ t x e n i 2 n t 2 sin 2 θ i 1 y e i ω t . It is interesting to note the effect of the term e n i 2 n t 2 sin 2 θ i 1 y in that expression. This is an exponential decay. The amplitude of the wave drops rapidly to zero.

So there is a transmitted wave but its amplitude drops precipitously. This is referred to as the evanescent wave.

Questions & Answers

what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
yes that's correct
I think
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get the best Algebra and trigonometry course in your pocket!

Source:  OpenStax, Waves and optics. OpenStax CNX. Nov 17, 2005 Download for free at http://cnx.org/content/col10279/1.33
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Waves and optics' conversation and receive update notifications?