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They're glasses that Benjamin Franklin had invented in 1784.
Bifocals have two different areas, with different focal planes. Normally split top to bottom, to allow the lower part to focus on reading.
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How is Benjamin Franklin remembered today?
Sadly, he is known more for flying a kite in the rain, than for the innumerable contributions he made to the making of the United States of America. Benjamin Franklin was a key contributor and his common sense approach towards the development of this country is under appreciated.
Where did Benjamin Franklin invent the biofocals?
Franklin was in Paris from 1777 to 1785. He first mentioned his bifocal lenses in 1784, and refers to them as "my invention" without giving any more detail. In 1779, he ordered some eye glasses, that were more time-consuming and expensive than normal, and it is POSSIBLE that the delay and cost were due to these being bifocal. A 1789 letter from a friend of Franklin states that Ben had been wearing double lenses for decades. In other words, the evidence is ambiguous. He might have invented them in Paris, or maybe while still in Philadelphia. Or he might have discovered them while in London, and simply claimed them as his idea.
What are the uses of concave lenses?
Uses of concave mirrors are:1) They are used in telescopes.2)They are used as dentists' mirrrors to magnify the image of a patients teeth to faciliate the examination.3)They are used as cosmetic mirrors to have an enlarged view of the face to apply make up or to shave.4) A Car Headlight bulb has a convex mirror.5)Make-up mirrors in department stores make you look skinnier than you really are.6.) Used as source of fire.7.)They are useful in projector lamps.
How has Benjamin Franklin affected your lives?
His discovery of electricity allows us to use anything electronic, such as video games and computers. His biofocals help the people that are a little blind see normally or better. His rods saves homes from lightning. ------------------------------------------------ (new dude) well... he did help make America independent so den the canadians may have not pwnd America in te OLYMPCS
