1986 Nobel Prize in Physics(1)
Reason for Award
for his fundamental work in electron optics, particularly for the design of the first electron microscope
Laureates
West Germany
Explanation
When we look at small things with a light microscope, we reach a limit because light waves are still too long. Ruska thought that using electrons, whose waves are much shorter than light, would allow us to see finer details. He bent and focused electrons with magnetic lenses and built the first electron microscope. Thanks to this device we can see objects far smaller than bacteria, such as viruses and the parts inside cells. The instrument is now used every day in science and medicine. That is why he received the Nobel Prize.
Related Keywords
Electron optics
Electron optics manipulates electron beams as waves using electric and magnetic fields to bend or focus them and form images. It parallels light optics, but charged electrons make magnetic and electrostatic lenses dominant. Higher accelerating voltages shorten the de Broglie wavelength dramatically, reducing the diffraction limit. Spherical and chromatic aberrations pose challenges, mitigated by multipole lenses and dedicated correctors. The field underpins applications from materials science to life science.
Electron microscope
An electron microscope exploits the short wavelength of electrons to attain resolutions beyond light microscopes. Several modalities exist, notably transmission and scanning forms, each suited to different tasks. Samples are placed in high vacuum and often require special preparation such as ultrathin slicing or conductive coating. The instrument is indispensable from virus morphology studies to semiconductor failure analysis. Aberration-corrected and energy-filtered systems now obtain atomic images together with chemical information.
de Broglie wavelength
The de Broglie wavelength characterises the wave nature of a particle and shortens as momentum increases. Accelerated electrons reach picometre wavelengths, key to the high resolution of electron microscopes. A shorter wavelength reduces diffraction blur, making inter-atomic distances observable. The idea also underlies techniques such as electron and neutron diffraction. It is a crucial bridge between quantum mechanics and measurement technology.
Electromagnetic lens
Electromagnetic lenses use fields from coils or electrodes to bend the path of electrons, playing the role of glass lenses in light optics. An axially symmetric magnetic field exerts a Lorentz force that focuses electrons in a spiral. Lens strength and aperture determine aberrations, and multipole configurations help correct spherical errors. The concept is applied not only in electron microscopes but also in accelerators and mass spectrometers. It is central to high-precision beam control.
Transmission electron microscopy (TEM)
TEM transmits an electron beam through a thin specimen, providing projection and diffraction images simultaneously. Phase contrast makes even light-element biomolecules visible. Energy filters enable elemental and valence mapping. Cryo-TEM combined with aberration correction now achieves atomic resolution in single-particle analysis. The method is indispensable for studying interfaces and dislocations in materials.
Resolution
Resolution defines the smallest separation at which a microscope can distinguish two points. In light microscopy it is limited to roughly 200 nm by wavelength and numerical aperture. Electron microscopes, with much shorter wavelengths, are theoretically capable of atomic resolution. Practical resolution is limited by aberrations, vibration and other engineering factors. Overcoming these limits is central to advanced microscope development.