Explain the first focal centre (first princip | vedclass

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(N/A) $1$. First Principal Focus $(F_1)$: It is a fixed point on the principal axis of a lens such that light rays starting from this point (in a conv

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(N/A) $1$. First Principal Focus $(F_1)$: It is a fixed point on the principal axis of a lens such that light rays starting from this point (in a convex lens) or appearing to converge towards this point (in a concave lens) become parallel to the principal axis after refraction through the lens.
$2$. Second Principal Focus $(F_2)$: It is a fixed point on the principal axis of a lens such that light rays coming parallel to the principal axis after refraction through the lens either converge to this point (in a convex lens) or appear to diverge from this point (in a concave lens).
- For a biconvex lens: The first focus is on the left side,and the second focus is on the right side.
- For a biconcave lens: The first focus is on the right side,and the second focus is on the left side.

Explain the first focal centre (first principal focus) and second focal centre (second principal focus) for a biconvex lens and a biconcave lens with the help of diagrams.

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