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Thread: Light

  1. #1 Light 
    Forum Senior anand_kapadia's Avatar
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    -It is known that light exhibhits both particle like and wave like properties.
    It is said that light consists of photons and they are emitted discontinuosly.
    This applise to Black body radiation and poto electric effect of light.
    But when it comes to interference and diffraction then what happens to these photons.
    Or is it just their properties at different instants.
    Then when interfernce of two waves happen how does these discontinuos waves(photon concept) produce such phenomenon

    -Is whitelight emmited from a tungsten bulb when passed through aprism emit just visible range of specrum or emits UV and IR rays too.


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  3. #2 Re: Light 
    Forum Junior Zitterbewegung's Avatar
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    Quote Originally Posted by anand_kapadia
    -It is said that light consists of photons and they are emitted discontinuosly.
    This applise to Black body radiation and poto electric effect of light.
    But when it comes to interference and diffraction then what happens to these photons.
    Or is it just their properties at different instants.
    Then when interfernce of two waves happen how does these discontinuos waves(photon concept) produce such phenomenon
    Whooops.....touchy subject here. Obviously the experimental setup -how we look at things- changes the outcome of this experiment.
    This is when philosophical considerations come into play. Way too complicated to fully discuss this here but there are basically two interpretations. The Koppenhagen interpretation and the many world theory.


    Quote Originally Posted by anand_kapadia
    --Is whitelight emmited from a tungsten bulb when passed through aprism emit just visible range of specrum or emits UV and IR rays too.
    Incandescent bulbs emit some UV light, but unless the glass envelope is made from quartz-glass most of this is already absorbed by the glass. And the UV part of the tungsten spectrum is only around .1 to .3% of the spectrum (energy-wise) so basically this can be neglected. The IR however is a different beast. Even the most efficient halogen incandescent bulbs only convert 5% of the electrical energy into visible light, the reast is IR. So actually the incandescent bulb is a little furnace that incidentally also emits some visible light.


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    Forum Senior anand_kapadia's Avatar
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    and what about the adio waves micro waves and so on.

    Also Sun is made up of Hydrogen and Helium So the spectrumof sunlight should be either of Hydrogen or of Helium Then why is it a continuos spectrum. And Does this light contains all the wavelengths of the electromagnetic spectrum.
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  5. #4  
    Forum Masters Degree SuperNatendo's Avatar
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    The sun emits not only visible light and heat, but also radio waves, x-rays, microwaves, pretty much every part of the electromagnetic spectrum.

    The chemical composition of the sun and the fusion of it's elements emit more of some parts of the electromagnetic spectrum than other parts of the spectrum, and different stars with a different composition will emit different amounts of certain parts of the spectrum than our star.

    There are more elements than just hydrogen and helium in the sun, even though they take up the majority of the sun's composition there are other elements that account for the emission of these other waves.

    I even read that in the atmosphere of the sun water vapor may exist:

    The coolest layer of the Sun is a temperature minimum region about 500 km above the photosphere, with a temperature of about 4,000 K. This part of the Sun is cool enough to support simple molecules such as carbon monoxide and water, which can be detected by their absorption spectra.

    From wikipedia:

    http://en.wikipedia.org/wiki/Sun

    The surface composition of the Sun consists of hydrogen (about 74% of its mass, or 92% of its volume), helium (about 24-25% of mass,[10] 7% of volume), and trace quantities of other elements, including Iron, Nickel, Oxygen, Silicon, Sulfur, Magnesium, Carbon, Neon, Calcium, and Chromium.[11]
    "It's no wonder that truth is stranger than fiction. Fiction has to make sense." - Mark Twain
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  6. #5  
    Forum Senior anand_kapadia's Avatar
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    The coolest layer of the Sun is a temperature minimum region about 500 km above the photosphere, with a temperature of about 4,000 K. This part of the Sun is cool enough to support simple molecules such as carbon monoxide and water, which can be detected by their absorption spectra.

    From wikipedia:

    http://en.wikipedia.org/wiki/Sun

    The surface composition of the Sun consists of hydrogen (about 74% of its mass, or 92% of its volume), helium (about 24-25% of mass,[10] 7% of volume), and trace quantities of other elements, including Iron, Nickel, Oxygen, Silicon, Sulfur, Magnesium, Carbon, Neon, Calcium, and Chromium.[11]

    And then if such molecules are present in the outer core then the sunlight should have an absoption spectrum rather than continuos one.
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  7. #6  
    Forum Junior Zitterbewegung's Avatar
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    Quote Originally Posted by anand_kapadia


    And then if such molecules are present in the outer core then the sunlight should have an absoption spectrum rather than continuos one.
    Herr Fraunhofer discovered those lines back in the 1850ies proving the general oppinion of that time - that there it will never be possible to gather information about the composition of stars - wrong.
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  8. #7  
    Forum Senior anand_kapadia's Avatar
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    Quote Originally Posted by Zitterbewegung
    Quote Originally Posted by anand_kapadia


    And then if such molecules are present in the outer core then the sunlight should have an absoption spectrum rather than continuos one.
    Herr Fraunhofer discovered those lines back in the 1850ies proving the general oppinion of that time - that there it will never be possible to gather information about the composition of stars - wrong.
    I didnot get what u said.
    Can u simplify it for me.
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  9. #8  
    Forum Junior Zitterbewegung's Avatar
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    There are in fact absorption lines in the spectra of each stars making it possible to analyze the composition. Mr. Fraunhofer discovered those lines named after him in the sun's spectrum around 1840something. Before that scientists thought it would never be possible to know the composition of a star.
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  10. #9  
    Forum Senior anand_kapadia's Avatar
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    Means they knew the composition of stars other than Hydrogen and Helium i.e. they found the trace elements.
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  11. #10  
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    Is all the light is same speed?
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  12. #11  
    Forum Masters Degree thyristor's Avatar
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    The speed of light in acertain medium is always constant but it varies from medium to medium in accordance with the refractive index for the material.
    373 13231-mbm-13231 373
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  13. #12  
    Forum Bachelors Degree martillo's Avatar
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    anand_kapadia:

    You should take a look on a new possible theory for your questions. May be you could find something interesting on it: www.geocities.com/anewlightinphysics

    Basically the theory recover the particle model of light showing that with the right structure for the particles all the known "wave-like" behaviors observed in Modern Experimental Physics can be succesfully explained.

    Wish you could find something good to inspire you making something great in Physics.
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  14. #13  
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    Quote Originally Posted by Zitterbewegung
    There are in fact absorption lines in the spectra of each stars making it possible to analyze the composition. Mr. Fraunhofer discovered those lines named after him in the sun's spectrum around 1840something. Before that scientists thought it would never be possible to know the composition of a star.
    Now if I view blue light through plexi glass. It will take longer for the plexi-glass to give off the light at the other end of the Plexiglas, once excited with a light source. Much slower then if I put that same blue light through quality glass.

    Yet when the two forms of light hit my eyes they will be going the same speed. After traveling through air to my eyes.

    Now how could that make sense? It cannot. There are rays going very fast that excite things to give off light. Those rays are racing at infinite speeds. They just create the excitement, in the object to give off light. We end up measuring the speed of light, by how much time it takes to create a light path, or excite an object. That is wrong.

    Sincerely,


    William McCormick
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