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2. 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 ?
3. Have electromagnetic waves any polarity?

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

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

very good... but the electric field (or magnetic) on EM waves has something like positive or negative signals?
6. 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:
7. 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
8. Derivation of Newton's F = ma: Help Needed

Hi, Anyone knows the derivation for Newton´s formula F = ma ? Any help is importante for me. Thanks
9. 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.
10. Finding the Deduction for Euler Number

Hi, Can anyone show me what´s the deduction for e Euler number ? Thank you
11. 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. Prerequisites for Learning Lagrangian Formalism in Quantum Field Theory

Hi, May anybody tell the pre-reqs (on calculus) for learn the lagrangian formalism used on quantum field theory ? :confused: Thanks.
13. Glass Transparency: What Allows Visible Light to Pass Through?

In the case of photochromatic lens, how the UV rays changes the molecular links between atoms ? are there any electron transitions ? Thanks.
14. Glass Transparency: What Allows Visible Light to Pass Through?

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

What´s the main difference between a metal and nonmetal in terms of atomic structure of elements ? :blushing: Thanks.
16. Mirror Reflexion: Does Photon Remain Unchanged?

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

Thanks but I didn´t find any satisfactory answer for that. Can anybody help me ?
18. Mirror Reflexion: Does Photon Remain Unchanged?

In case of mirror reflexion, a photon reflected is the same ? There´s some atomic process in this fenomena ? :blushing:
19. 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.
20. 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...
21. 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. 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.
23. 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