noun
ultramicroscope
A specialized optical instrument used to observe particles smaller than the wavelength of visible light, often in colloid science. Technical term.
限外顕微鏡はコロイド粒子の観察に使われる。
An ultramicroscope is used to observe colloidal particles.
General term for microscope; 限外顕微鏡 is a specific type that uses scattered light to view sub-wavelength particles.
Compound of 限外 (beyond the limit) and 顕微鏡 (microscope), likely a calque from English 'ultramicroscope'.