If fv and fR are the focal lengths of a convex lens for violet and red light respectively and Fv and FR are the focal lengths
If fv and fR are the focal lengths of a convex lens for violet and red light respectively and Fv and FR are the focal lengths of a concave lens for violet and red tight respectively. then we must have
(a) fv > fR and Fv > FR
(b) fv < and Fv > FR
(c) fv > fR and Fv < FR
(d) fv < fR in and Fv < FR.
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Correct option (b) fv < and Fv > FR
Explanation:
For a convex lens, fR > fv or fv< fR. For a
concave lens, focal length is negative.
.'. |Fv| < |FR| or Fv > FR as the smaller negative value is bigger.
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