Questions

Benjamin Franklin has long been credited with the invention of bifocal lenses and he was the first to wear bifocal lenses. He did not produce them himself but instead had some optician in London or France make them for him to overcome Presbyopia, a condition that Franklin suffered. He was tired switching between lenses for far and near sightedness. And that resulted in inventing Bifocal Lenses.

Turbines are machines powered by rotating blades.

Robert Brown, Scottish botanist, Discovered The Nucleus of a Cell in 1831, London. When Brown was studying orchids under microscope when he observed an opaque area, which he called the "Areola" or "Nucleus", in the cells of the flower's outer layer.

The nucleus was also described by Franz Bauer in 1804 but in detail Robert Brown made it in 1831.

Covalent type of bonding joins The two hydrogen atoms are joned by Covalent type of bonding.

In this type of bonding, electrons are shared between the atoms in order to fill there valence shells. Thus sharing of electrons take place in between the hydrogen atoms.