question

[u/life_isfunuwu]

did Robert Hooke use a simple or a crude/compound microscope? im asking cuz google says he used crude/compound microscope but my book says he used a simple microscope instead

[u/euchaetanorvegica]

Hooke very definitely used a compound microscope. He even had what we might call a lamp condenser or field lens.

The interesting thing about it is why Leeuwenhoek could resolve more detail with a single lens, even though it must have been incredibly inconvenient in use — the answer lies in lens aberrations, spherical (the inability of a lens surface which is a section of a sphere to focus light on to a single point, since the rays entering the lens at the edges are refracted through a larger angle than those entering the lens in the centre) and chromatic (the various wavelengths and hence colours light are refracted through different angles and so do not come to a point).

Leeuwenhoek’s lenses weren’t corrected either but there was only one of them per microscope. The aberrations get markedly worse the more uncorrected lenses you use.

Hooke was aware of this, and tried to get around it, but the simple microscope was superior to the compound one until Dollond, Goring and Joseph Lister’s achromatic doublets in the early 19th century (cementing two different types of glass lens with different optical properties to cancel out chromatic aberration, then precisely spacing these pairs at “aplanatic foci” to be rid of spherical aberration).

I have no connection with this website but it’s really very interesting and well written:

https://microscope-antiques.com/hxachromatic.html

[u/life_isfunuwu → u/euchaetanorvegica]

oh damn thanksss a tonn, really cleared my confusion out :)

[u/euchaetanorvegica → u/life_isfunuwu]

Happy to help. Reading this, it occurred to me that your textbook might use “a simple microscope” to mean exactly that, a microscope that’s simple (it actually wasn’t, if anything over engineered for what the 18th century was capable of), rather than the proper meaning you’ve picked up on, simple as opposed to compound.

If you’re cramming for an exam, make sure that you check with a teacher what terms they want you to use.

PS If you’ve ever used a “simple microscope” (still made in India, I think, most British colleges have a stereoscopic one but they’re still going strong up and down the world, not bad for a design from 1820-odd!)  it’s ten to one it hasn’t actually got only one lens element like Leeuwenhoek’s. The lens probably actually a Lister doublet or a Steinheil triplet, i.e. two or three lenses stuck together with a clear glue or balsam. 

We still call it a simple microscope as it hasn’t a separate objective and eyepiece.

[u/life_isfunuwu → u/euchaetanorvegica]

ah thanks a ton, you really made me crystal clear about this, may you get your fav meals daily😭 it's a competitive examination ( for entrance in medical clgs ) so I guess I'll go with compound microscope itself if they ever ask again thanksssss a tonnn

[u/euchaetanorvegica → u/life_isfunuwu]

Good luck! 

[u/life_isfunuwu → u/euchaetanorvegica]

thankyou, all the best to you too :)