Who is credited with inventing bifocal lenses, which combine two different optical powers in a single spectacle lens?

Introduction / Context:
As people age, they often need different optical powers for near and distant vision. Bifocal lenses solve this by combining two lens powers in one spectacle lens. This question asks which historical figure is credited with inventing bifocal lenses and using them personally in daily life.

Given Data / Assumptions:

• The invention is bifocal lenses for spectacles.
• Bifocals combine two sections, one for distance and one for reading.
• The options list prominent figures from the early history of the United States.
• We assume a basic awareness that some political leaders were also inventors and scientists.

Concept / Approach:
Benjamin Franklin, one of the Founding Fathers of the United States, was also a scientist and inventor. He is widely credited with inventing bifocal lenses so that he would not need to switch repeatedly between two pairs of glasses. His bifocals had the upper part for distance and the lower part for reading, a design principle still used today.

Step-by-Step Solution:
Step 1: Recognise that among the listed names, Benjamin Franklin is the one most associated with scientific experimentation and invention. Step 2: Recall that Franklin conducted experiments on electricity and also created practical inventions such as the lightning rod and bifocal spectacles. Step 3: Connect this memory with the need for two different lens powers being combined in a single frame to create bifocals. Step 4: Therefore, the inventor of bifocal lenses is Benjamin Franklin.

Verification / Alternative check:
You can verify by recalling that John Adams, James Madison and Thomas Jefferson are primarily remembered for their political roles and writings, not for optical inventions. Franklin stands out as the statesman inventor. General knowledge books frequently mention his bifocal lenses as an example of his practical approach to daily life problems, confirming that he is the correct choice.

Why Other Options Are Wrong:

• John Adams: A political leader and second President of the United States but not noted for inventing bifocals.
• James Madison: Known as the Father of the US Constitution, not for optical inventions.
• Thomas Jefferson: Famous for political leadership and architecture but not for creating bifocal lenses.
• Isaac Newton: A great physicist who studied optics but is not associated with bifocal spectacle design in everyday use.

Common Pitfalls:
Sometimes students see Isaac Newton in an option list and choose him for any question involving optics. However, this question is about a practical spectacle invention and also features names from American political history. Recognising Benjamin Franklin as both a statesman and an inventor helps avoid this mistake and leads you to the correct answer.

Final Answer:
Bifocal lenses were invented by Benjamin Franklin.