Magnification of images

On a previous page, we saw that the ratio of image height to object height was

The negative sign means that the image is inverted if di is positive, which means the image is in front of the mirror and hence real. Thus we find a general rule: Real images are inverted, virtual images are upright. (This rule is not necessarily true in situations where more than one lens or mirror is present, because in that case the "object" for one lens or mirror is an image produced by another lens or mirror, which can be behind it, making do negative.)

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