The fundamental property of a convex lens Z is that it converges light rays. If the object is in different positions in front of the convex lens, the light emitted by the object will converge differently through the convex lens, that is, the properties of the object image will be different. Therefore, convex lenses are widely used in our life.

1.Slide projector, projector and film projector

The lens of the slide projector is also equivalent to a convex lens. The distance from the transparent slide to the lens is slightly larger than the focal length of the lens. By shining strong light on the slide, the picture on the slide can be projected onto the screen to form an inverted and enlarged real image. In order for the audience to see the upright image, the slides are inserted upside down on the shelf. The structure of a projector commonly used in teaching is similar to that of a slide projector.

The main difference is that the projector uses two large plastic threaded lenses as concentrators (the threaded lenses act as convex lenses) and a flat mirror to reflect the image onto the screen. The projector can project large picture slides or text written directly on transparent film, making it easy to use. The film projector is a further improvement of the slide projector, its film can be continuously moved, and the addition of sound, enhance its audio-visual effect.The

2.The microscope

The magnification of a magnifying glass is usually only a few times, but not more than 20 times. If you want to further improve the magnification, you need to use a microscope. The tube of a microscope has a convex lens at each end. The convex lens close to the eye is called the eyepiece, and the convex lens close to the object being observed is called the objective.

The object through the objective lens into an enlarged real image, and then through the eyepiece into an enlarged virtual image, after two amplification, so the magnification is increased. So doctors often use a microscope to observe the composition of the patient’s blood to diagnose the disease; It is used in plant classes to explore the characteristics of cells in different parts of plants and to understand their associated physiology.

3.The telescope

When watching the Olympic Games, you have to use a telescope to see farther away. An ordinary telescope is equipped with a convex lens and a concave lens at both ends of the glass tube, while an astronomical telescope is equipped with a convex lens at both ends of the glass tube. The focal length of the objective lens is long, and the focal length of the eyepiece is short. Such a telescope has a wider field of view, which is especially suitable for observing planets and the moon.

In addition, there are many problems related to the “convex lens” in life. In the forest, tourists may cause forest fires if they discard transparent round drink bottles filled with water everywhere. This is because the bottle acts as a convex lens, which causes the sun’s rays to converge. It is best not to cover the haystack with plastic film.

The plastic film after the water is equivalent to a convex lens, which has a convergent effect on the sunlight and is easy to ignite the grass. Through the round water cup to see calligraphy and painting, calligraphy and painting is enlarged, the round water cup is equivalent to a convex lens, it has the effect of magnification. The triangular shape of the thermometer, in which a convex surface acts as a convex lens, also plays the role of magnification, so that it is easy to see the temperature, etc.

How to buy a good telescope?

So today we’re going to look at lenses in telescopes.
1, do not excessively pursue high magnification: 7-10 times is the best choice, more than 10 times, in the equipment will be heavy, it is not easy to carry
2, moderate caliber: as a soldier, generally choose 40-50mm caliber. In the peripheral hardware as a small caliber is better.
3, eyepiece must be big: eyepiece big watch rise comfortable a lot, say from optical Angle additionally, eyepiece big mirror, enter pupil light can be much, luminous rate is high, clarity is also high. On MARKET, IN low end mirror is small EYEpiece more, high-end and top mirror is to play EYEpiece.
4, the field of view must be large: a mirror with a small field of view looks very uncomfortable. View at 1000 meters, try to reach more than 110 meters, preferably above 130 meters. The field of view is inversely proportional to the multiple and directly proportional to the caliber. But even more important is the design of the inside of the binoculars. The same multiple, the same caliber mirror, the field of view will be very different.
5, clarity, high brightness: this needs to feel, or look at the experience of others. The metrics are hard to see.
It can be said that convex lenses are everywhere in life. It is because of its existence, as well as its unique role, make life more colorful.