two ray metting at a point forming a slice is called__
Answers
Step-by-step explanation:
Let us consider the formation of image of a point by a thin convex lens. (See figure)
One thing is certain that image of a point will be a point only.
The main point is to locate the position of the image point.
We know that when at least two lines(rays) intersect each other a point is fixed . So, we shall have to take at least two rays from the object point P. These rays are so selected such that they necessarily pass through the lens and their paths after they pass through the lens can be ascertained easily.
Therefore , in the figure we have taken one ray parallel to the axis of the lens. For such ray we are sure that after passing through lens it will pass through the focal point of the lens. But this single ray( geometrically line) will not fix the point we are in search of. Therefore , we have to take an another ray from point P. This ray is again so chosen that it’s path can be determined easily. For this reason we take this ray passing through the optical center of the lens. The ray passing through optical center does not get deviated and proceeds further in the same direction. The intersection of these two rays gives a point, Q. Now, if we take more number of rays from point P then they will also have to pass through Q only after passing through the lens, otherwise we shall have large number of images of a single point by a thin convex lens. So, only two rays are enough.
If we consider reversibility of path of light, then also we can see that Q must be image of point P.
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