When parallel rays exit a concave lens, the light rays are divergent.
The rays diverge or bend away from the axis it has been traveling upon entering the lens when it reaches the other side of the lens. These rays appear to have come from the same focal point before entering the concave lens. When these parallel rays are extended, it will be traced back to a single point of origin.
Answer: electron on the shell of the atom
Explanation: that what I trying to remember
Williamson synthesis is the most common way for obtaining ethers, called after its developer Alexander Williamson. It is an organic reaction of forming ethers from an organohalide and an alkoxide. The reaction is carried out according to the SN2 mechanism.
On the attached picture it is shown required alkoxide ion, <span>alkyl(aryl)bromide and the ether that forms from the reactants. </span>