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Case 2: An Object Closer to the Lens (but still outside F1):
Here is the lens diagram, with the object already in place, and the first ray drawn:  Notice that the object is still outside F1, but within twice the focal distance. Also, when drawing the first ray of light, we followed the first principle, that a ray hitting the lens parallel to the base line will refract through the focus. Now let's draw the second ray. It will pass through the focus on the left side first, then refract in the lens and emerge parallel to the base line.  The point at which these two rays intersect will give us the top of the image (since the rays came from the top of the object). Here is the diagram:  This time the image, while still inverted, is noticeably larger than the object. In other words, the object has been magnified ... its image appears bigger. the image appears upside down and larger than the object. You can also observe this phenomenon with a magnifying glass. Again, hold the lens up so that light from the bulb passes through and onto the paper. This time, hold the lens closer to the bulb. The image appearing on the paper will again be upside down, but larger than the original bulb! Try it and see! But this can't be what happens when you use a magnifying glass to enlarge something, because you don't see it upside down. Moreover, you seem to see the image as being on the same side of the glass as the object; both situations so far have shown an image on the opposite side of the glass as the original object. There must be another case we haven't looked at yet! |