When and how was the magnifying glass invented

How does a magnifying glass work?


Magnifying glass

A magnifying glass is also known as a magnifying glass. It essentially consists of a convex converging lens, which is usually attached to a handle. Magnifying glasses are used to look at very small things that normal eyesight can no longer see properly (e.g. postage stamps, small print, etc.)

Why does a magnifying glass magnify?

The converging lens of a magnifying glass creates a "virtual image", which is shown correspondingly larger on the retina in the eye. In the following graphic you can see above the normal view of an object that is shown relatively small on the retina. Below, the magnifying glass creates a virtual image that is shown much larger on the retina.


How a magnifying glass works

How a magnifying glass works

A magnifying glass works like a converging lens (convex). The focal point is behind the lens - and everything in front of the focal point is shown enlarged. The reason for this is a "virtual image" that is created by looking into the magnifying glass. The size of the virtual image varies due to different distances - between eye and magnifying glass or between magnifying glass and object.


Converging lens (biconvex)

If the object is further away than the focal point, the object is mirrored, i.e. it appears upside down.

History of the magnifying glass

The ancient Egyptians recognized the principle of the magnifying glass - they discovered the magnifying effect of water droplets on leaves. In principle, such a drop of water acts like a lens that refracts the light. The drop enlarges what lies behind it.

The Roman scholar Seneca the Younger described the magnifying effect of water in the 1st century AD.

Around 1000 AD, the Arab mathematician and optician Abu Ali al-Hasan ibn al-Haitham, Latin called Alhazen, described a similar aid in his book "Treasure of Optics": a polished, transparent hemisphere enlarges the letters when you use them with the smooth side on a book.


Reading stone (Photo: Ziko van Dijk)

In the Middle Ages, monks were the custodians and advancers of knowledge - and everything that had to do with it. Only: the aging monks, like people today, suffered from a natural, age-related visual impairment: presbyopia. Alhazen's work was translated into Latin around 1240 and found its way into monastery libraries. These are lenticular, transparent, plane-convex stones made of glass that could be placed on top of texts, which gave them a magnifying effect. Basically, the reading stones were the forerunners of today's magnifying glasses.

These stones or the knowledge that was gained from them were then consistently further developed. This resulted in all the optical instruments and devices that we know today: magnifying glasses, microscopes, telescopes, cameras and so on.

Here you can find free magnifying glass graphics and search icons for free download.

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Reading magnifier

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Magnifying glass