Question

When were bifocal lenses invented?

Answer 1

We are asked about the invention of the bifocal lens. We can start to attempt this question by defining what a bifocal lens is. Then we can move onto stating how the bifocal lens was invented, by whom, and why they were invented.

Complete answer:
We can start to answer this question by defining a bifocal lens. Bifocal lenses, as the name suggests are one eyeglass with two values of focal length or power. We can say two values of power as power can be defined as the reciprocal of focal length.

These lenses have the correction (for the vision defect) on the top of the lens and the ones that help you read are on the bottom. They are often used to correct presbyopia along with myopia or astigmatism. This invention enabled numerous people to live an easier life. It helped people resolve both distance vision as well as near vision problems.

The bifocal lens was invented by Benjamin Franklin in the year $1784$.

Note: Benjamin Franklin was born in $1706$ in the city of Boston. He was a publisher, scientist, inventor and a diplomat. He helped in the drafting of the US constitution, He invented the bifocal lens, lighting rod etc. Some people believe that he invented electricity because he proved that lighting is electric by using a kite and at the end of it, a key was tied to see the conduction of electricity. This experiment enabled him to invent the lightning rod which is now used in ships and buildings.