alleryThe power of a lens is −2.5 D. The lens is
Aconcave, focal length 25 cm
Bconvex, focal length 40 cm
Cconcave, focal length 40 cm
Dconvex, focal length 2.5 cm
Answer & Solution
Correct answer: C. concave, focal length 40 cm
Negative power → diverging → concave lens.
$f=1/P=1/(-2.5)=-0.4$ m $=-40$ cm; magnitude 40 cm.
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