Exploring Light Interference and Interferometry

 
Interference and
interferometry
 
By R Seguin
What is light interference?
 
Remember sound interference?
 
Its like that but with light. Simple as that.
the Path Length Difference equals some number multiplied
by the wavelength and we have different levels of
interference depending on what that number is PLD = m
λ
 
When two waves of light converge they can cause the light
we see to change just like how sound interference changes
the sound we hear
Its often caused by diffraction
Examples of interference
 
Young’s double slit experiment
Supernumerary rainbows
Those rainbow colors formed by oil on water or soap bubbles
 
Double slit experiment
 
The double slit experiment is  a
very classic way to view
interference of light
 
But is easier to do in theory than
experimentally since the distance
between the slits has to be very
small
 
Those other things I mentioned
 
Supernumerary rainbows are the lighter rainbows inside
the main rainbow created by the interference of  the
light coming out oat different angles from the water
droplets.
 
Thin film interference is formed  by some of the light
reflecting off of the top of the film while other light
reflects off the surface under the film thus creating
a difference in the distance traveled by the two
waves putting them out of phase.
 
Math
 
Double slit formula: dsin
θ
 = m
λ
 this only holds if d and a are both
very small distance and D is much much larger than both
 
Thin film: 2n
2
dcosθ
2
 = m
λ
 using Snell's law we can
use  n
1
sin(θ
1
) = n
2
sin(θ
2
) to find θ
2
 
general rule: PLD = m
λ we have complete constructive interference when m = n = {0,1,2,3…} we will have
perfect destructive interference when m = n + 0.5
 
What is interferometry?
 
Interferometry is a general term for
sciences that use the interference of
electromagnetic waves to collect data.
Interferometry is quite wide reaching
with uses in fields from astronomy to
medicine.
Because the maximum interference
values happen every time the path
length difference is half a wavelength
and the wavelength of light is very small
we can make very precise readings but
these devises are easily disturbed by any
nearby vibrations.
 
Diagram of an interfferometer
 
Gravitational waves
 
First hypothesized by albert Einstein (although we don’t know how much
work was done by his first wife Mileva Maric) in 1916 in the general theory
of relativity. Essentially they are ripples in space-time created by dramatic
changes in how n object is affecting spacetime like a supernova collapsing
into a black hole or a massive object with a huge acceleration moving
towards another massive object. These waves are some of the weakest
forces in the universe needing one of the most sensitive of measuring
devices ever created to observe even the most powerful of GWs
 
Laser Interferometer Gravitational-Wave
Observatory
 
The observatory consists of two massive
interferometers. One located in Hanford Washington
and one in Livingston Louisiana. The reason they are
so far apart is so local vibrations can be ruled out
while looking for the same interference at the same
time from both locations, then that data is sent to
other observatories to see if they got similar results.
Each arm of these interferometers are 4km long
On September 14 2015 LIGO observed actual
physical affects of gravitational waves for the first
time
Thee waves were caused by two black holes
colliding but by the time they reached earth they
only moved space-time an less than the diameter of
a proton.
 
Holographic interferometry
 
This type of interferometry involves the superposition of holograms of
a object that is being studied.
 
Any movement of the object causes interference
 
this movement can be caused by vibration, heating,  stress, etc.…
 
analyzing this interference can give information about the object
 
Sample test question
 
Light of wavelength 510nm is traveling  at a thin film of oil on top of water at an
angle of 60° above the horizontal. the refractive index of air is 1.00 and the index of
oil is 1.46. what is the first 3 thicknesses d of the film of oil for which we would
have complete destructive interference?
 
Bibliography
 
 
 "Double Slit Interference." 
Slit Interference
. Hyperphysics, n.d. Web. 30 May 2017.
<http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/slits.html>.
 
Hariharan, P. 
Basics of Interferometry
. Amsterdam: Elsevier, 2007. Print.
 
 "holographic interferometry." 
The Penguin Dictionary of Physics
, edited by John Cullerne,
Penguin, 4th edition, 2009. 
Credo Reference
,
http://www.student.wvc.edu:2548/content/entry/pendphys/holographic_interferometry/0.
Accessed 30 May 2017.
 
 "Learn More." 
LIGO Lab
. Caltech and MIT, n.d. Web. 30 May 2017.
<https://www.ligo.caltech.edu/page/learn-more>.
 
 "Oil Film Interference." 
Thin Film Reflection and Interference
. Hyperphysics, n.d. Web. 30
May 2017. <http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/oilfilm.html>.
 
Serway, Raymond, and John Jewett. "Interference of Light Waves." 
Physics for Scientists
and Engineers
. 7th ed. N.p.: Cengage Learning, 2007. 1051-099. Print.
 
 Wolf, Emil, and Max Born. 
Principles of Optics: Electromagnetic Theory of Propagation,
Interference and Diffraction of Light
. Oxford: Pergamon, 1970. Print.
 
 Young's Double Slit Introduction
. Dir. David SantoPietro. 
Khan Acadeny
. Youtube, 07 July
2014. Web. 29 May 2017. <https://www.khanacademy.org/science/physics/light-
waves/interference-of-light-waves/v/youngs-double-split-part-1>.
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Discover the fascinating world of light interference and interferometry through examples like Young's double slit experiment and supernumerary rainbows. Understand how the path length difference affects interference levels and delve into the applications of interferometry across various scientific fields. Uncover the principles and formulas behind interference phenomena, from thin film interference to the double slit experiment.


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  1. Interference and interferometry By R Seguin

  2. What is light interference? Remember sound interference? Its like that but with light. Simple as that. the Path Length Difference equals some number multiplied by the wavelength and we have different levels of interference depending on what that number is PLD = m When two waves of light converge they can cause the light we see to change just like how sound interference changes the sound we hear Its often caused by diffraction

  3. Examples of interference Young s double slit experiment Supernumerary rainbows Those rainbow colors formed by oil on water or soap bubbles

  4. Double slit experiment The double slit experiment is a very classic way to view interference of light But is easier to do in theory than experimentally since the distance between the slits has to be very small

  5. Those other things I mentioned Supernumerary rainbows are the lighter rainbows inside the main rainbow created by the interference of the light coming out oat different angles from the water droplets. Thin film interference is formed by some of the light reflecting off of the top of the film while other light reflects off the surface under the film thus creating a difference in the distance traveled by the two waves putting them out of phase.

  6. general rule: PLD = mwe have complete constructive interference when m = n = {0,1,2,3} we will have perfect destructive interference when m = n + 0.5 Math Thin film: 2n2dcos 2 = m using Snell's law we can use n1sin( 1) = n2sin( 2) to find 2 Double slit formula: dsin = m this only holds if d and a are both very small distance and D is much much larger than both

  7. What is interferometry? Interferometry is a general term for sciences that use the interference of electromagnetic waves to collect data. Interferometry is quite wide reaching with uses in fields from astronomy to medicine. Because the maximum interference values happen every time the path length difference is half a wavelength and the wavelength of light is very small we can make very precise readings but these devises are easily disturbed by any nearby vibrations. Diagram of an interfferometer

  8. Gravitational waves First hypothesized by albert Einstein (although we don t know how much work was done by his first wife Mileva Maric) in 1916 in the general theory of relativity. Essentially they are ripples in space-time created by dramatic changes in how n object is affecting spacetime like a supernova collapsing into a black hole or a massive object with a huge acceleration moving towards another massive object. These waves are some of the weakest forces in the universe needing one of the most sensitive of measuring devices ever created to observe even the most powerful of GWs

  9. Laser Interferometer Gravitational-Wave Observatory The observatory consists of two massive interferometers. One located in Hanford Washington and one in Livingston Louisiana. The reason they are so far apart is so local vibrations can be ruled out while looking for the same interference at the same time from both locations, then that data is sent to other observatories to see if they got similar results. Each arm of these interferometers are 4km long On September 14 2015 LIGO observed actual physical affects of gravitational waves for the first time Thee waves were caused by two black holes colliding but by the time they reached earth they only moved space-time an less than the diameter of a proton.

  10. Holographic interferometry This type of interferometry involves the superposition of holograms of a object that is being studied. Any movement of the object causes interference this movement can be caused by vibration, heating, stress, etc. analyzing this interference can give information about the object

  11. Sample test question Light of wavelength 510nm is traveling at a thin film of oil on top of water at an angle of 60 above the horizontal. the refractive index of air is 1.00 and the index of oil is 1.46. what is the first 3 thicknesses d of the film of oil for which we would have complete destructive interference?

  12. Bibliography "Double Slit Interference." Slit Interference. Hyperphysics, n.d. Web. 30 May 2017. <http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/slits.html>. Hariharan, P. Basics of Interferometry. Amsterdam: Elsevier, 2007. Print. "holographic interferometry." The Penguin Dictionary of Physics, edited by John Cullerne, Penguin, 4th edition, 2009. Credo Reference, http://www.student.wvc.edu:2548/content/entry/pendphys/holographic_interferometry/0. Accessed 30 May 2017. "Learn More." LIGO Lab. Caltech and MIT, n.d. Web. 30 May 2017. <https://www.ligo.caltech.edu/page/learn-more>. "Oil Film Interference." Thin Film Reflection and Interference. Hyperphysics, n.d. Web. 30 May 2017. <http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/oilfilm.html>. Serway, Raymond, and John Jewett. "Interference of Light Waves." Physics for Scientists and Engineers. 7th ed. N.p.: Cengage Learning, 2007. 1051-099. Print. Wolf, Emil, and Max Born. Principles of Optics: Electromagnetic Theory of Propagation, Interference and Diffraction of Light. Oxford: Pergamon, 1970. Print. Young's Double Slit Introduction. Dir. David SantoPietro. Khan Acadeny. Youtube, 07 July 2014. Web. 29 May 2017. <https://www.khanacademy.org/science/physics/light- waves/interference-of-light-waves/v/youngs-double-split-part-1>.

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