Microscope

[Primarygun]

When we use high-power lenses, the image goes dimmer, why?

[YT2095]

the quantity of photons hiting any particular sample is limited, the more you magnify a particular part, the less photons are being sellected to create the image.

 

if 100 photons illuminate an object evenly that is the size of your finger, how many will be seen if you just look at your finger nail? 20 maybe?

so it appears dimmer

 

btw, the above example doesn`t represent TRUE quanties! it`s demo purpose only

[Firedragon52]

I'm not if it also has something to do with the fact that lights wavelength, for resolution, decreases as well.

[YT2095]

I'm not if it also has something to do with the fact that lights wavelength, for resolution, decreases as well.

maybe I`m having a "Blonde moment" here, but I don`t understand that at all?

[badchad]

I think he meant to say that because of lights wavelength, you can only achieve a finite resolution with a light microscope.

 

Specifically, I think it has to do with the amplitude of light. I vaguely remember learning it in the following way:

 

imagine two particles sitting very close to one another; particles one and two: (1)(2).

 

if the wave of light cannot "fit" between the two particles, you won't be able to tell there is two (no matter what magnification you use). This is why electron microscopes are superior. The wavelength of light is smaller, and can "fit between" a small space, thus increasing the resolving power. This is also why you need to use oil immersion at higher power, the oil changes the properties of the wavelength of light.

 

Sound about right?

[YT2095]

it sounds like under illuminated types that may apply to (the "to fit Through part" makes me think that). it doesn`t apply to the above illumnated types though, whereas photon quantity divided by and to fill the Objective lens becomes less as the magnification increases

[badchad]

Yeah, maybe I was unclear. I agree on the reason for images becoming dimmer as magnification increases.

 

The "fit through" remark was made in response to firedragon, and the resolution of light VS. electron microscopes.

[YT2095]

Electron Microscopes!... I think I`ve missed something here?

[badchad]

lol, I may be getting confused too....

 

I started my part of the discussion (which in all honesty had little to do with the original question of why higher magnification leads to dimmer light) in response to firedragon's quote, which I've attempted to edit for clarity.

 

I'm not sure but it also has something to do with the fact that lights wavelength, for resolution, decreases as well.

 

Essentially, I went off on a slight derail of how the resolution of a microscope is related to the wavelenght of light that is used to view the specimen.

 

I used the example of an electron microscope to illustrate my point which in a nutshell is that electron microscope's have a greater resolution than light microscope, because the wavelength or "size" of a stream of electrons is smaller than that of light. The smaller "size" of the "electron stream" which is used in electron microscopy would be better able to fit between two closely spaced specimens. Thus, resolving that there are two specimens, instead of one.

[YT2095]

n/p

 

btw, the oil`s used for up close hi-mag not only as a lens itself but a more stable media than Air as a light channel, a wavelength change (if any) is purely incidental and has no bearing on results

[Primarygun]

Only light microscope give coloured image, right?

[YT2095]

as far as I know, yes. all the electron types that I`ve seen have all been grey scale. but there may have been new advances since then?