27 questions · 15 almanac · 0 findings

Electron Microscopy

Imaging at atomic and molecular resolution using electron beams.

Almanac Borrowing Electrons to Beat Light
  • Why can't optical microscopes resolve detail finer than about half the wavelength of visible light?
  • How did Ruska and Knoll use magnetic fields to focus electrons the way glass lenses focus light?
  • Why was a magnification of only seventeen times still considered a breakthrough in 1931?
  • What kinds of structures became visible for the first time once electron microscopes surpassed optical instruments?
Almanac Watching a Living Cell Think
  • Why were transparent cells nearly invisible under a conventional light microscope before phase contrast?
  • How does phase-contrast microscopy convert an invisible phase shift in light into visible contrast?
  • Why did staining or fixing a specimen make it impossible to observe certain living processes?
  • Why did it take Zeiss engineers nearly a decade to build Zernike's design into a working instrument?
Almanac No Law Forbids the Very Small
  • What technologies that Feynman's lecture anticipated, like atomic-force microscopes and molecular machines, didn't exist yet in 1959?
Almanac A Gap Smaller Than an Atom
  • Why can electrons resolve finer structure than visible light in a microscope?
  • How does quantum tunnelling let a scanning tunnelling microscope map individual atoms?
  • Why did Ernst Ruska wait fifty-three years between his invention and his Nobel Prize?
  • How did the scanning tunnelling microscope open the door to nanotechnology?
Almanac A Suggestion, Not a Law
  • What is Abbe's diffraction limit and why did it seem to cap microscope resolution at around 200 nanometres?
  • How does STED microscopy use a second laser to sharpen resolution below the diffraction limit?
  • How can switching individual fluorescent molecules on and off one at a time reconstruct a nanometre-scale image?
  • What kinds of cellular structures became visible for the first time once super-resolution microscopy existed?