1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Curious question about light/photons

Tags:
  1. Feb 17, 2016 #1
    Hi there,

    If a photon wavelength (yellow) is isolated from the other wavelengths that sunlight emits (once it gets to earth), can that particular particle/photon be distorted slightly into a wavelength that is shorter (perceived as green)?

    If yes; please explain.
    If no; please explain.

    Thank you!
     
  2. jcsd
  3. Feb 17, 2016 #2

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    What does "isolated" mean here?

    To perceive it as green, you need (a) a rocket moving towards sun at relativistic speeds or (b) a neutron star or black hole, blueshifting the wavelength. Not so practical.
     
  4. Feb 17, 2016 #3
    I guess my responses to your answer are:

    1. Can you separate/isolate certain wavelengths of light from the total spectrum that our star gives off (after that light goes through our atmosphere)?

    2. If that isolated light has a wavelength of about 570 nm (yellow) can it be manipulated or distorted to equal a slightly shorter wavelength of about 510 nm (green)?

    Please explain why if yes or no, if possible.

    Thank you so much,
     
  5. Feb 18, 2016 #4

    blue_leaf77

    User Avatar
    Science Advisor
    Homework Helper

    Use the so-called monochromator, which basically consists of a light decomposer (e.g. diffraction grating or prism) followed by a slit to let through only the wavelength of interest.
    It might be possible by utilizing Raman anti-Stokes scattering.
     
  6. Feb 18, 2016 #5

    ChrisVer

    User Avatar
    Gold Member

    you can filter the wavelengths when you observe them on the Earth.. there are different types of filters that allow certain wavelengths to go through them.

    mfb already gave the answer.... 1 of them was the Doppler effect on light to measure a different wavelength [itex]\lambda_m[/itex] than the oiginal source's one [itex]\lambda_o[/itex]...
     
  7. Feb 18, 2016 #6

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    You can also collect the sunlight with a solar cell and operate a light bulb with its electricity. I'm just not sure if that counts. You can also send the photon through a few million acousto-optic modulators, neglecting the efficiency issue.

    All those things are not slight modifications. Most of them capture the light and then produce new light.
     
  8. Feb 18, 2016 #7
    Does a monochromator weaken the energy of the desired frequency?
     
    Last edited: Feb 18, 2016
  9. Feb 18, 2016 #8
    This application requires i stay put.. Are you saying that mfb answered the only ways that one frequency of light can be distorted into another frequency?
    In the doppler effect and in a rocket, that is relativistic, not practical, am i right? Please explain, if possible.
     
  10. Feb 18, 2016 #9
    Can you please explain how it would be possible using this and if any energy is lost in the process? Thank you
     
  11. Feb 18, 2016 #10
    It appears that the "acousto-optic modulators" use radio frequencies and sound waves, so im guessing that there will be loss of energy in this scenario?

    Is there any way to use a material to physically distort red light (650 nm) to be 651nm?, possibly by speeding up its wavelength through a medium or any other way to prevent loss of energy?
     
  12. Feb 18, 2016 #11

    blue_leaf77

    User Avatar
    Science Advisor
    Homework Helper

    A monochromator necessarily reduces the total beam energy because you are extracting a group of photons having certain small frequency interval out of the entire input bandwidth.

    The energy levels diagram for this process looks like
    250px-CARS_diagram.png
    Here you need two input beams, one with frequency ##\omega_{pump}## (which is equal to ##\omega_{probe}##, so the pump and probe beams have the same frequency) and another one with ##\omega_{Stokes}##. The two frequencies are chosen such that ##\omega_{pump}-\omega_{Stokes} = \omega_{vib}##. The material is first excited by ##\omega_{pump}## to a virtual level (left dotted line), then ##\omega_{Stokes}## beam triggers stimulated emission of frequency ##\omega_{Stokes}## bringing the medium to a higher level than the starting one. Then the medium is re-excited by the probe beam to another virtual level (right dotted line). Upon going back to the starting level, the medium emits a light of frequency ##\omega_{CARS}## which is larger than the input ##\omega_{pump}##. You can find more about this process by searching Coherent Anti-Stokes Raman Scattering (CARS).
     
  13. Feb 18, 2016 #12
    Definitely. So, of the desired frequency interval that i choose, will there be a loss of energy within that frequency or will that frequency remain unchanged? Also, is there a way to filter the desired frequency WITHOUT dispersing the rest of the electromagnetic spectrum? In the end, i would like to marry them back together actually.

    (I will research CARS right now, thank you very much)
     
    Last edited by a moderator: Feb 18, 2016
  14. Feb 18, 2016 #13

    blue_leaf77

    User Avatar
    Science Advisor
    Homework Helper

    A loss of energy may come from the efficiency of the monochromator, if a prism is used, then the main loss is due to the reflection on the faces of the prism. If a grating is used, then the fact that the beams are separated into different diffraction orders upon diffracting limits the efficiency.
     
  15. Feb 18, 2016 #14

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    No, it just blocks all frequencies apart from a narrow range. Well, at least for an ideal monochromator.

    This sounds like an x-y-question. What do you actually want to do?
     
  16. Feb 18, 2016 #15
    Haha, after reading this: http://meta.stackexchange.com/questions/66377/what-is-the-xy-problem
    You might be right.

    2-fold:

    1. I want to explore possible creation of a basic Arithmetic Logic Unit for a CPU inspired design, deconstructed of course. By isolating sections of the electromagnetic spectrum i hope to channel (at first) 6-8 different fixed frequencies with a starting point and ending point (spatially) Point A to Point B. With code, and then CPU, frequency will at point B represent computations from Point A by effectively raising, lowering or staying the same the frequency between point A and B. The end result basically would have thus have created a computation represented by the degree of change in frequency leading to; output from the Arithmetic Logic Unit. I can go more into depth with this if you would like, its a bit hard to put into writing without explaining the method of computations and processes i would like to tackle after success of this feat. In a CPU the ALU is what does the grunt work, and its difficult to keep pace for other components to store that information. (this is after the ridiculous cramming of near atomically measured systems). However: (http://gizmodo.com/a-new-light-based-memory-chip-could-change-the-fundamen-1731307674) and other ways to store light were created, thus giving the possibility to eventually fully eliminate the 0 & 1 binary system down the line and develop a new system with infinite degrees of exponential assignments, exponential computations, results, and possibly compute faster than basically anything, with minimal use of conventional devices.

    Meeting with physics teachers, professionals in the field, and other trusted people has generated great excitement between us, but also lead me to some other exciting thoughts:

    2. If you could manipulate the spectrum of light that is of significance to creating sustainable energy, with less loss of energy than standard methods of deriving power from light (photovoltaics or others), you could potentially:
    a. divorce each frequency-or-'sections of frequency' into respective filters
    b. shorten each sections wavelength in an incremental and respective step sequence
    c. marry the energy back together at a single shortest frequency possible, thus forcing greater energy efficiency generated entirely from sunlight.
     
  17. Feb 18, 2016 #16
    Light is an electromagnetic force. Or one effected by magnetism. That is why it is given a "frequency". How do you tune a radio frequency to one you desire? The same principle can be applied to tuning light frequencies. Lights frequencies can be received just as radio frequencies can. It all depends upon your receiver's ability to convert the signals into what you want to tune. In short, you have to convert light into a prismatic range of frequencies that are presented to you. Once you do that you can select the one you want. You then amplify this into a projection device to achieve your color. The projection device should be able to do this conversion by identifying the frequency as given to it and referenced to the spectrum of light. The prism in the device would match the total wavelengths of white light and only project that light selected by the frequency sent to it.
     
  18. Feb 19, 2016 #17
    I'm a little unclear on the question and I'm no where near qualified to add to this since I don't even have my Bachelors yet but I'll give it a whirl.
    I think what you're asking is; is there any way we can manipulate wavelengths of colors to perceive the world in a different color?
    I think the answer is no. Since we are talking about light here you have a photon moving at speed c (the speed of light) with a frequency and a wavelength. In order to change the wave length and make it go down (shorter) you have to change the frequency(higher) to make it stay at the speed of light. So we would have to be moving towards the sun at an incredible velocity. I don't know how correct I am on this. Just some late night thoughts.
     
  19. Feb 19, 2016 #18

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    Why do you want to change the frequency? Changing intensity or polarization is so much easier. And even that is a very challenging task. Optical computing has some interesting applications, mainly for fast internet data transfer (where the data transmission is optical already, so you save two conversion steps). I don't think replacing a whole ALU or even the whole CPU with optical elements is a realistic option in the near-term future.
    You cannot reduce entropy, and you cannot violate conservation of energy either. Upconversion of infrared light for photovoltaics is studied, but multiple layers sensitive to different wavelength ranges are possible as well.
     
  20. Feb 21, 2016 #19
  21. Feb 21, 2016 #20

    davenn

    User Avatar
    Science Advisor
    Gold Member

    so, It's taken 19 posts for you to get to the core of what this thread is all about

    you said "we" ... are you stating that you are part of this engineering team ?

    and what does this new info have to do with your original Q ?


    Dave
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Curious question about light/photons
  1. Questions about photons (Replies: 12)

Loading...