There are three principal rays. The first principal ray occurs when the light comes in parallel to the principle axis, it goes out through the focus. The second principal ray occurs when light comes in through the focus, then it comes out parallel to the principle axis
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Answer:
There are three principal rays. The first principal ray occurs when the light comes in parallel to the principle axis, it goes out through the focus. The second principal ray occurs when light comes in through the focus, then it comes out parallel to the principle axis