Thread: Microscopes, resolution, wavelength and amplitude

This question concerns optical and electron microscopes. We are taught that shorter wavelengths allow improved image resolution. Is it not possible to have a longer wavelength with tiny amplitude that can fit between "the gaps" to provide a better image? A biologist trying to understand physics...

So far as I know electron microscopy[in it's original form] does not rely on wavelength, it uses a beam of electrons finely focussed onto the object. Detectors then detect secondary electron emission from the target. This continous stream is then amplified many times to produce an image. Since electrons are very small the resolution is high. Optical microscopes are mostly restricted by distortions in the lensing system.

Originally Posted by billco

So far as I know electron microscopy[in it's original form] does not rely on wavelength, it uses a beam of electrons finely focussed onto the object. Detectors then detect secondary electron emission from the target. This continous stream is then amplified many times to produce an image. Since electrons are very small the resolution is high. Optical microscopes are mostly restricted by distortions in the lensing system.

sorry, i don't understand. isn't the "beam of electrons" related to wavelength?

Shorter wavelengths basically mean higher frequency (if we let the speed remain constant) wavelength=speed/frequency. Higher frequency means better resolution.

Amplitude is related to the strength of the signal, a high amplitude signal will be brighter and clearer.

So far as I know electron microscopy[in it's original form] does not rely on wavelength, it uses a beam of electrons finely focussed onto the object. Detectors then detect secondary electron emission from the target. This continous stream is then amplified many times to produce an image. Since electrons are very small the resolution is high. Optical microscopes are mostly restricted by distortions in the lensing system.

haha, electrons HAAVE WAVELENGHT

erm.. I think miniroll was talking about the optical microscope

Originally Posted by montager

Originally Posted by billco

So far as I know electron microscopy[in it's original form] does not rely on wavelength, it uses a beam of electrons finely focussed onto the object. Detectors then detect secondary electron emission from the target. This continous stream is then amplified many times to produce an image. Since electrons are very small the resolution is high. Optical microscopes are mostly restricted by distortions in the lensing system.

sorry, i don't understand. isn't the "beam of electrons" related to wavelength?

It is a continuous stream of electrons, the beam itself has no frequency component, if your T.V is of the electron tube type, that too uses a stream of electrons, focussed and generated by the same principles as an electron microscope. The difference with the T.V however is that the beam current varies to vary brightness[I accept that a color tv has three electron guns]. An optical microscope as I said is mostly dependant upon the quality of it's lens system.

Originally Posted by zelos

haha, electrons HAAVE WAVELENGHT

Would you care to educate me as to where this has any relevance to scanning electron microsocopy?

Originally Posted by vmstudent

erm.. I think miniroll was talking about the optical microscope

Really?

Originally Posted by miniroll

This question concerns optical and electron microscopes.

To clarify what Billiard was saying, f = cp/wavelength.
Where 'f' is the frequency, 'c' is the speed of light, and I'll leave Zelos to tell you what the 'p' is as well as answer my previous question to him.

Would you care to educate me as to where this has any relevance to scanning electron microsocopy?

thats the very fundamental phenomena the electron microscope is based on. Without that phenomena electron microsope wouldnt exist

Come on then, explain it to me!

You can even read about it in your favourite site.
http://en.wikipedia.org/wiki/Electron_microscope

If by some chance you are more familiar with this subject than I am, then explain it, simply writing things like "ha ha you're wrong" is plain bloody stupid.

you found it youself, read it

So where did this poor blind senile old fart miss the word 'frequency' on that page?

Tell me smart ass If I connect a battery and bulb and cause current to flow in the circuit, what is the frequency of that current?

and you have still not answered the other question about the 'P' in my formulae above...

Zelos, IF you believe my explanations above are incorrect then please answer the original question, I have an excellent knowledge of EM and nothing you have said leads me to believe it is either wrong, or has been superseeded.

the frequens is 0 in a battery

f = cp/wavelength

this formula? i am not familiar with it, p usualy detonates momentum wich is mv

the wavelenght of matter is:
wavelenght = h/p=h/mv
where h is plancks constant and m is amss and v is velocity

Originally Posted by Zelos

the frequens is 0 in a battery

f = cp/wavelength

this formula? i am not familiar with it, p usualy detonates momentum wich is mv

the wavelenght of matter is:
wavelenght = h/p=h/mv
where h is plancks constant and m is amss and v is velocity

It is one of the fundamental formulae used in Electronics.

Your are right that in a battery the frequency would be Zero. it is a DIRECT CURRENT

The beam Current in an electron microscope is also a DIRECT CURRENT, and therefore 0Hz

It is the focussing ability of the gun that determines the resolution of an electron microscope. The second primary detractor of resolution is vibration. The electron Microscope in my lab (in the early 70's) was set on a 3 metre thick concrete base, insulated from the rest of the building. On many occasions we used it at night, traffic on a motorway some 1 KM away was sufficient to rule out many sensitve measurements being made during the day. Since the original question was on resolution that is how I answered the question.

Once again, IF you have a better answer than mine please explain.

The beam Current in an electron microscope is also a DIRECT CURRENT, and therefore 0Hz

its different you senile old man. Thats classical stuff we are talking abouta quantum phenomena. All matter no matter how big have a wanelenght/frequens according tot he formula wavelenght=h/mv thats where the electrons wavelenght comes from

Very well , answer his question, explain exactly how you would improve resolution, which was his question.


Miniroll, are you still there? - what do you think..


In fact Zelos, I take such offence you language, I'll go and find another form.

Since you began talking about there being a wavelength in a direct current, I must add that we also are all equally "old farts", according to carbon dating aswell, ever thought of that Zelos? :-D

Originally Posted by miniroll

This question concerns optical and electron microscopes. We are taught that shorter wavelengths allow improved image resolution. Is it not possible to have a longer wavelength with tiny amplitude that can fit between "the gaps" to provide a better image? A biologist trying to understand physics...

The shorter wavelength gives us better resolution in the same way that a sharp pencil can give us better resolution than a blunt pencil. Continuing with this analogy, the amplitude is kind of like how hard you press, it doesn't improve resolution as such, too low an amplitude would mean that the image would be too faint to see.

Note however that each photon is a discrete bundle of energy, it is quantized, you cannot vary the amplitude of a single photon.

In fact Zelos, I take such offence you language, I'll go and find another form.

dont play all knowing then wich you try sometimes

ever thought of that Zelos

our atoms yes, our molecules, no. Our cells, absolutly NOT

Note however that each photon is a discrete bundle of energy, it is quantized, you cannot vary the amplitude of a single photon.

but you can do it with electrons by increasing their speed

In fact Zelos, I take such offence you language, I'll go and find another form.

hurray