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 .