What are the characteristics of convex lens imaging? The focal length of the convex lens

Cat's eye is a small optical instrument installed on the door of a house, which is convenient for residents to observe the outdoor situation. It is a necessity for home safety. Curious children must be wondering what kind of lens it is? For example, the common myopia glasses in life are concave lenses. They are caused by the reflection of light and are a virtual image. They have a divergent effect on light. Are you inspired?

Contents of this article

1. Is the cat's eye a convex lens or a concave lens?

2. Convex lens imaging characteristics

3. Focal length of convex lens

Is the cat's eye a convex lens or a concave lens?

The cat's eye is composed of a concave lens and a convex lens. The focal length of the objective lens is extremely short, which makes the outdoor person or object form a positive and reduced virtual image, which falls exactly within the focus of the eyepiece, and finally obtains a reduced positive virtual image.

The cat's eye is composed of an objective lens and an eyepiece, just like a telescope or a microscope. The objective lens is a concave lens, and the eyepiece is a convex lens.

Cat's eye is a small optical instrument installed on the door of a house, which is convenient for residents to observe the outdoor situation. It is a necessity for home safety.

When you look out through the peephole from indoors, you can see the scene outside the door within a field of view of about 120 degrees, but you cannot see inside the door through the peephole from outside the door.

Convex lens imaging characteristics

The imaging of a convex lens is mainly a refraction imaging. The image formed is an inverted, reduced, or inverted, equal-sized real image, which has a converging effect on light. Its lens is very thin on both sides and very thick in the middle. The image formed can be seen directly with the naked eye or received by a light screen.

Convex lens imaging is an optical law. It is a refraction imaging of light. The image formed can be an inverted, reduced real image, or an inverted, equal-sized or enlarged real image. It is an image formed by the re-convergence of actual light produced by refraction or reflection, and has a converging effect on light.

At the same time, the convex lens is very thick in the middle and very thin on both sides, and is mainly convex in shape. The image it forms is real and can be viewed directly with the naked eye and received on a light screen. When imaging, the object and the lens are on opposite sides. Common farsighted glasses are convex lenses.

In addition, the principles of convex lenses and concave lenses are opposite. The myopia glasses lenses commonly seen in life are concave lenses. They are formed by the reflection of light and are a virtual image. They can only form upright and reduced images, and have a divergent effect on light. The lens is very thin in the middle and on both sides.

Focal length of convex lens

Focal length, also known as focal length, refers to the distance from the center of the lens to the focal point where light gathers. Convex lenses can make light parallel to the main optical axis converge at one point, which is called the focus. The distance from the focus to the optical center is called the focal length. There are two real focal points on a convex lens, one on the left and one on the right.

Method for measuring the focal length of a convex lens. Place the convex lens facing the sunlight, put a piece of white paper on the other side of the convex lens, and adjust the distance between the convex lens and the white paper so that a smaller and brighter light spot appears on the white paper. This light spot is the focus. Use a ruler to measure the distance from the convex lens to the focus, which is the focal length.