Who invented the first compound microscope?
(a) Robert Hook
(b) Robert Koch
(c) Leeuwenhoek
(d) Z. Janssen

Hint:

The first compound microscope was developed by a father and son team. The son, a teenager, received help from his father, Hans, in constructing this early microscope. The device used two lenses—one positioned near the object and another as the eyepiece.

Complete Answer
            The correct answer is (d) Z. Janssen. 

Zacharias Janssen, a spectacle maker, discovered that by placing lenses at specific distances in a tube, he could achieve magnified views of objects. This early lens system, which involved positioning one lens close to the object and another near the eye, led to the basic design used in modern microscopes and telescopes.

• Anton van Leeuwenhoek, often referred to as the father of microscopy, was known for crafting high-quality lenses. As a cloth merchant, he required lenses with fine resolution to examine fabric details. Leeuwenhoek produced lenses with high curvature, achieving up to 270x magnification—the highest at that time—and was the first to observe and describe bacteria, yeast, and blood circulation in capillaries. 
• Robert Hooke, another influential figure in microscopy, validated Leeuwenhoek’s findings. Hooke made enhancements to the light microscope and contributed significantly to early studies of microorganisms. 
• Robert Koch made groundbreaking discoveries in bacteriology, identifying the causative agents for diseases like tuberculosis, cholera, and anthrax. His work provided experimental support for the theory of infectious disease.

Additional Notes

• The earliest known microscope, attributed to Janssen, dates back to 1595 and is preserved in a museum in Middelburg, Europe.
• Janssen’s microscope featured a sliding tube design with lenses that could magnify images three to nine times.
• In 1609, Galileo Galilei improved on the microscope’s design and named it the “occhiolino” or “little eye.”