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Focal Length of a Lens
The value of the focal length of the lens is equal to the value of the image distance when rays are (A) Passing through optical center(B) Parallel to the principal axis.(C) Passing
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Focal length, explained by RP; focal distance, dioptric power, curved mirror, lens equation, microscope, photographic objective, focus, beam radius
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Concave lens: Principal focal length – be careful
