The prism lens image virtual image
In optics, the actual light to form an image, called reality, can undertake with light screen; instead, it is called virtual image, only by eyes. The physics teacher with experience, tells the difference in the real image and virtual image, often mention such a distinction: "real image is inverted, and the image is erect. The so-called "upright" and "inverted", is of course with respect to the original object.
Three kinds of image plane mirror, convex and concave lens formed, is upright; and the concave mirror and convex lens into reality, and the reality of the pinhole imaging, without exception is inverted. Of course, the concave mirror and convex lens can become two kinds of virtual image and virtual image, they become, the same is erect state.
Then the human eyes in the image is real or virtual? We know that the structure of the human eye is equivalent to a convex lens, then the external object formed in the retina of the image must be real. According to the experience of the images on the retina seems to be inverted. Any object but we usually see, it is erect? Conflict and the "rule", actually involves adjusting functions of cerebral cortex and life experience.
When the focal length of the object and the convex lens is greater than the distance between the lens is less than two times, the object inverted image, when the object from far to near the lens, like gradually become larger, as to the distance between the lens becomes big gradually; when the object and the distance between the lens focal length is less than when the object is amplified into a like, is an illusion.
When the object and the convex lens distance is greater than two times, the object images be inverted, this is like a candle at the convex lens light through the convex lens and the actual light focal point, can undertake light screen, is real. When the object and the distance between the lens focal length is less than when the object into an image.