Virtual vs Real Images
Virtual and real images are two kinds of images that are apparent reproduction of real objects formed by a mirror or a lens. These images are formed through processes of reflection, refraction or diffracted rays of light. In a real image, light rays are brought to a focus at the position of the image. The most important aspect of image is that a real image can be made visible on a screen such as a sheet of paper whereas a virtual image cannot be produced on a screen. Some common examples of real images are those made by a camera lens on film or the images made by a projector lens on the screen of a cinema hall. There are some more differences between a real and a virtual image that will be discussed in this article.
Virtual images are made by rays that do not actually come from where one sees the image. For example, in the case of an image formed by a plane mirror it is situated at some distance behind the mirror and not where it seems to an onlooker. This is why it is called a virtual image.
Talking of lenses, a real image is formed when light rays originating from a point on one side of the lens are refracted by the lens so that they focus to a point on the other side of the lens at the image location. This takes place when the object is at a distance greater than the focal length of the lens. On the other hand, when light rays originating from one side of the lens are refracted by the lens so that they diverge on the other side of the lens, a virtual image is formed. Virtual image formation has a requirement that the object must be at a distance less than the focal length of the lens.
In order to see an image on a screen light rays must come to a focus on the screen. But in the case of a virtual image, there are no actual light rays coming together at the location of the virtual image which is why one cannot see a virtual image on screen.
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In brief: • While real image appears inverted, virtual image appears erect • While real image can be obtained on a screen, virtual image cannot be seen on a screen. • In case of mirrors, real image lies in front while virtual image lies behind the mirror. • In case of lenses, real image lies on the other side of the object whereas virtual image lies on the same side of the object.
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