Ultra
Thin Films
Films
having thickness below 100 Ao.
Ultrasonic Waves
Sound waves of high frequency greater than 20,000 Hz
are called as ultrasonic waves. These frequencies are beyond audible limit.
Umbra
(Latin for
“shadow”) is the innermost and darkest part of a shadow, where the light source
is completely blocked by the occluding body.
Uniaxial
Crystal
It is a double
refracting crystal which has only one axis along which both the refracted rays
have same speed. Ex: Calcite, Quartz, etc.
Uniform
Circular Motion
The motion of an object with constant speed
in a circle.
Unit
Cell
Basic structural
unit or building block of crystal structure, which defines the crystal structure by virtue of
its geometry and the atom positions within it. A unit cell is chosen to
represent the symmetry of crystal structure, where in all the atom positions in
the crystal may be generated by translation of unit cell integral distances
along each of its edges.
Universal
Gravitational Constant
It is the force between two unit masses
separated by unit distance is called universal gravitational constant. The
value of ‘G’ is 6.67 x 10-11 Nm2Kg-2.
Unsaturated
Vapor
If a liquid is in open container, the vapor
molecules rapidly diffuse away from liquid, and in general produce unsaturated
vapor.
