Measuring distance of a planet using parallax method
Similarly, α = d / D
Whereα = angular size of the planet( angle subtended by d at earth) and d is the diameter of the planet. αis angle between the direction of the telescope when two diametrically opposite points of the planet are viewed.
Measuring very small distances
To measure distances as low as size of a molecule, electron microscopes are used. These contain electrons beams controlled by electric and magnetic fields.
o Electron microscopes have a resolution of 0.6 Å or Agstroms. o
Electron microscopes are able to resolve atoms and molecules while using tunneling microscopy, it is possible to estimate size of molecule.