Light and Optics

[MedGrl@2022]

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I have a couple questions regarding Light and Optics. On page 142, Examkrackers, says the energy of a single photon is given by E=hf. But then it gives a warning that states: “Do not be mislead by this equation: The equation gives the energy by photon. It turns out that if we double the frequency, we also double the number of photons increasing the intensity by a factor of four as expected.” Why does the number of photons increase when we increase the frequency? Is the increase of the in the number of photons directly proportional to the increase of the frequency?

Also, I have a question regarding chromatic dispersion. I thought that the velocity of a wave was constant and the only thing that could change it is the medium. However, EK says that in chromatic dispersion, “longer wavelengths (lower frequencies) move faster through a medium than shorter wavelengths (higher frequencies), and therefore bend less dramatically at the media interface.” Do the waves change their velocities when changing a medium because frequency stays constant and wavelength changes? Thus, all wavelengths become shorter due to the new medium having a higher index of refraction? And the waves are all moving at a slower velocity but because there were some light waves that already had a higher frequency they move slower because their wavelengths are slower? Why isn’t the effect of the medium change similar to all the different light waves and thus result In all waves moving at the same velocity?

Thank you,

Verónica

 

[sdm33]

The number of photons does not increase when we increase the frequency, only the energy increases with the increase in frequency, each electron can absorb only one photon at a time, increasing the intensity will not increase the kinetic energy of the photoelectrons ; it will increase the number of photoelectrons
E = hf
KE max = f - work function

 

[MedGrl@2022]

The number of photons does not increase when we increase the frequency, only the energy increases with the increase in frequency, each electron can absorb only one photon at a time, increasing the intensity will not increase the kinetic energy of the photoelectrons ; it will increase the number of photoelectrons
E = hf
KE max = f - work function

I am still confused why is EK saying that "if we double the frequency, we also double the number of photons increasing the intensity by a factor of four as expected.” They did not mention electrons. I don't think electrons are mentioned in this chapter. It refers to E=hf as the energy of a single photon not electron. I am still confused... ??? :-/

Thanks for trying to help. Maybe someone can clear this up.

 

[milski]

I am still confused why is EK saying that "if we double the frequency, we also double the number of photons increasing the intensity by a factor of four as expected.” They did not mention electrons. I don't think electrons are mentioned in this chapter. It refers to E=hf as the energy of a single photon not electron. I am still confused... ??? :-/

Thanks for trying to help. Maybe someone can clear this up.

Could you explain a bit further what the context is? You cannot just double the frequency without some sort of interaction. I don't have EK - are they describing some sort of experiment?

 

[sdm33]

Einstein, in 1905, when he wrote the Annus Mirabilis papers you can read that might help, also I like your picture if you can rotate it a little bit, every time i turn my head omg i feel dizzy. lol