Where is the difference between reading glasses and magnifying glass?

➤Is reading glasses and magnifier the same lens? What are the similarities and differences between the two? Can I use the magnifying glass as a reading glasses directly on my eyes? 

In the first picture, a grandfather with reading glasses holding a magnifying glass is reading the newspaper with relish. This picture of great significance in life seems to be using facts to describe the relationship between the two.

                                                  Figure 1                                      Figure 2

By observing strokes, we know that reading glasses and magnifiers are all based on the principle of light refraction made of thick, thin edge convex lens. 

Convex lens has a convergence effect, also known as a converging lens, parallel rays (such as sunlight) parallel to the main optical axis (the connecting line of the spherical centers of the two convex spherical lenses) into the convex lens, refracted through the convex lens will be concentrated on the shaft point, The focal point of the convex lens (marked as F). 

The convex lens has a focus on both sides of the mirror. For the thin convex lens, the distance between the two focal points and the center of the lens (optical center) is approximately the same, which is called the focal length of the convex lens. 

The radius of the convex lens is The smaller the focal length, the shorter. The same object placed in different positions through the convex lens will be a different image, as shown in Fig. 3.

When the object is within the focal length of the convex lens (point A in the figure), it is a virtual image enlarged in the positive direction, such as a magnifying glass. When the object is between the 1x focal length and the 2x focal length of the convex lens (point B in the figure), it is an inversely magnified real image, such as a projection slide projector. When the object is outside the focal length of 2 times the focal length of the convex lens (point D in the figure), it is an inverted real image, such as a camera. 

It is not difficult to see from the law of convex lens imaging that when using a magnifying glass, the object must be placed within the focal length. At this time, the convex lens is the virtual image of the object. The farther the magnifying glass is from the object, the larger the virtual image; the higher the magnification is. Magnifiers require a thicker center of the lens and the lens area can be smaller. 

Reading glasses do not generally require multiples that are too high, and the lenses are relatively large, so that they can have a large field of view to facilitate reading. If the object distance exceeds 1 times the focal length, the image will become inverted. And need to be observed on the other side.

                                                                         Figure 3

The lens of the eye is equivalent to a convex lens. It also works by using the principle of inverting and reducing the real image when the object distance is greater than 2 times the focal length, as shown in Fig. 4, however, the eye looks at distant objects or near objects not by changing the object distance. Or as the distance to achieve (because the distance between the lens and the retina is essentially the same); it is to change the focal length of the lens by the ciliary muscles to change the focus of the lens so that the image accurately falls on the retina, the retina Light shines through the nerves to the brain to figure out what this "object" is. 

After the age of 40, the lens of the human eye becomes progressively fibrotic, and the ciliary muscles become less stretchable. As a result, the eyeballs become shorter and the focusing ability of the lens system is also weakened. 

The result is that distant objects are clearly seen, and objects close to them are blurred. At this time, the state of the eye is called presbyopia; the effect of focusing by means of a convex lens can be supplemented by the adjustment of the reading glasses so that the image of the object falls on the retina .

Magnifier main thing is to put the imaging large people to see more clearly, not for vision correction, normal seeing subtle things can also use a magnifying glass; and reading glasses is the root according to the individual eye diopter different and fitting in order to allow The image of the object is better imaged on the retina, for the purpose of seeing things.

Both magnifying glass and reading glasses belong to the convex lens. If the commonly used magnifying glass is converted into reading glasses, it is equivalent to 1000-2000 degrees (glasses power is equal to 100 times the focal length of the focal length), obviously not suitable for individuals, if long-term use of magnifying glass instead of reading glasses It can cause eye soreness, swelling, headaches, etc., and can even seriously damage the eyes. 

Therefore, reading glasses need to be prepared scientifically after professional optometry, and reading glasses cannot be randomly worn. Magnifiers are only suitable for short-term use and in some special occasions. Use, and science to wear reading glasses can be suitable for a variety of occasions.

With the explanations of the difference between reading glasses and magnifying glass, we hope it is helpful to you!
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