What's magnifier:

The simple visual optics used to observe the details of the object is a converging lens with a focal length much smaller than the photopic distance of the eye. The size of an object imaged on the retina of the human eye is proportional to the angle (angle of view) the object opens to the eye. The larger the viewing angle, the larger the image, and the more you can distinguish the details of the object. Moving closer to the object can increase the viewing angle, but it is limited by the eye's ability to focus. Use a magnifying glass to make it close to the eye and place the object within its focus to form an erect virtual image. The function of the magnifying glass is to enlarge the viewing angle.

Precautions for using magnifying glass:
1. Be careful not to collide with hard objects such as steel to prevent the magnifying glass from breaking;
2. Do not face your skin under strong light to prevent burns or cause fire to flammable materials;
3. Don't put it naked in humid air.