Recent content by amylase

Homework Statement In photoelectric effect, why does photon prefer K shell electron? Asked differently: In photoelectric effect, why does photon prefer electron of closest binding energy, rather than going for another electron of much lower binding energy? Homework Equations...

As title. Thank you. In the context of MRI, why/how does applying 90 degree radiofrequency at Lamour frequency put proton precessions into phase? I understand 90 degree RF minimises net magnetic moment, such that there is least difference between number of protons in parallel (with...

Thanks guys. Really appreciate all the input. Suppose for the original solid white box picture, X-axis is labelled "X coordinate of pixel" and Y-axis is labelled "X coordinate of pixel". Z axis is "brightness of pixel at coordinate (x,y)". @ DaleSpam: Thanks for the links. I had a play with...

Cool. Thank you very much (and everyone who replied!). So if I'm recording a natural, real world phenomenon, like a live concert, as long as I am sampling at >= 2f the concert's highest frequency f then I can reconstruct back to exact original. That's clear to me now. However if the original is...

Just to set the scene, Paul Bouke's webpage shows, this picture as the original signal: Viewed in intensity versus coordinates mode (spatial domain) is like this: Viewed in frequency domain looks like these: So that's where I'm coming from. I can't understand the spike picture, how that is...

Hi DaleSpam, thanks a lot for the reply. I guess when I asked "how do you do it", I meant "if you use a software to do it, how would that software do it? ie. what would be its step by step algorithm?". Thanks a lot for the links. They have very nice pictures. That kind of half make sense to me...

Hey thanks guys for the replies. @ f95toli: What do you mean "The more frequency components you retain, the better the re-construction"? Do you mean even if I sample at 2f, I still won't be able to reconstruct back to the exact original signal? I think this is where I have some misconception. I...

Pretty sure I have some misconceptions, please correct me thanks. SHORT VERSION According to Nyquist's theory, if I want to digitally record a live opera and be able to reconstruct back to exactly the original sound quality, I have to sample at at least twice the frequency of the original...

(This may sound like home work but it's not) What does it mean to display a picture in its frequency domain? A solid square box becomes a star shape? SHORT VERSION As title thanks. Firstly, what does it mean to show a picture in its frequency domain? and secondly, how do you do it...

Hi smartCH Thanks for clarifying a few things and recommended book. I still don't understand though, why does attenuation decrease as intensity increases? I can understand at low energy the effect is mainly from photoelectric effect, at medium energy (of hundrends keV) the effect is...

Hi Drakkith, thanks for the reply. Intensity the way I intended was energy content per photon. Going back to your first sentence, Why would shorter wavelength decrease absorption? I would have thought shorter wavelength is even more easily absorbed... :S

Hello. Not sure if this is the right board to post. This is not homework. I am just self-teaching quantum physics as I read a book on the topic of X-ray Physics. It has about 30 chapters in total and so far I find myself having about 3 questions per chapter. Hope you guys don't mind me asking...