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  1. L

    Limits and continuity

    A very good book. See also
  2. L

    How photon interact with electron ?

    Hi, How can a photon interact with a electron (ex. Compton scattering) whether the photon has no sign like positive ou negative charges? How the field (EM wave) in the photon interact with a electron ?
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    Have electromagnetic waves any polarity?

    But can an EM wave emitted by the proton interact with electron ?
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    Have electromagnetic waves any polarity?

    Only the electron particle can emit and interact with EM waves ?
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    Have electromagnetic waves any polarity?

    very good... but the electric field (or magnetic) on EM waves has something like positive or negative signals?
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    Have electromagnetic waves any polarity?

    Hi, My doubt is how can the EM waves interact with an electron, i.e., electron is a particle with negative charge.. have EM waves any charge to attract or to repulse an electron ? :confused: An example is the microwaves oven when waves interact with water molecules. Thanks :smile:
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    Harmonic motion with friction x(t)=

    harmonic motion with friction x(t)=... Homework Statement Anybody knows what´s the equation x(t)=... for harmonic motion with friction ? Homework Equations For exemple, a string-block sistem with friction ? I need determine the position of block at t instant. The Attempt at a Solution
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    Derivation for F = ma

    Hi, Anyone knows the derivation for Newton´s formula F = ma ? Any help is importante for me. Thanks
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    How can a photon became a electron ?

    Hi, Is there any simple answer to the fenomena where a photon can became a electron ? can we use the E = mc2 for that ? Thanks for any help.
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    Finding the Deduction for Euler Number

    Hi, Can anyone show me what´s the deduction for e Euler number ? Thank you
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    About tension (is this correct ?)

    If I want to know the tension on strings is possible use the algebra below ? \SigmaFx = cos\theta T2-T3 = 0 and \SigmaFy = sen\thetaT2-T1 = 0 so T2=T3/cos\theta and T2 = T1/sen\theta so T1cos\theta = T3sen\theta is this correct ? Thanks obs: this is not my home work, but a...
  12. L

    Lagrangian formalism

    Hi, May anybody tell the pre-reqs (on calculus) for learn the lagrangian formalism used on quantum field theory ? :confused: Thanks.
  13. L

    Glass transparence

    In the case of photochromatic lens, how the UV rays changes the molecular links between atoms ? are there any electron transitions ? Thanks.
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    Glass transparence

    What´s glass feature (molecular structure) that allow the visible light bypass it ? :confused: Thanks
  15. L

    Metal and nonmetal difference

    What´s the main difference between a metal and nonmetal in terms of atomic structure of elements ? :blushing: Thanks.
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    Photon reflexion

    I mean, is the photon "reflected" at atomic level ? There´s a magnetic fenomena in this ?
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    EM radiation cross over materials

    Thanks but I didn´t find any satisfactory answer for that. Can anybody help me ?
  18. L

    Photon reflexion

    In case of mirror reflexion, a photon reflected is the same ? There´s some atomic process in this fenomena ? :blushing:
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    EM radiation cross over materials

    Anybody knows if there is a rule for EM radiation cross over materials ? The wavelenght in comparison the size (or structure) of molecule is determinant ? Ex. why infrared pass through the concrete but not metalics ? Thank you.
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    Formula for sphere surface

    Sorry, I did not say, but I would like not to use calculus for this, just geometry or algebra for demonstration. For exemple: the triangle area is: A_{t} = \frac{b h} { 2 } if I put a triangle inside a circle, where the top of it is the centre of circle, and I use infinity number of...
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    Formula for sphere surface

    4 Pi r2 I know this formula, but anyone knows, how can I figure out (by methods, algebra) the sphere surface formula ? Thanks
  22. L

    How can a atom generate photons ?

    But is not a photon emited when a electron of this ion change energect level ( in orbit ) ? I did imaginate that molecules from material collides ( because temperature ) each other, making electrons change betwen energy levels.
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    How can a atom generate photons ?

    I don´t understand how can an excited atoms generate photons, ex. a incandescent lamp. Does vibrating eletrons emit eletromagnetic fields ? Thanks a lot