An achromatic convergent doublet has power of +2D. If power of convex lens is + 5D, then ratio of the dispersive powers of a convergent and divergent lenses will be
Answer & explanation
Correct answer: option 1
$P = +2D$ $∴ P_1=+5D$ $∴ P_2=-3D$
As $\frac{P_2}{P_1}=\frac{f_1}{f_2}=-\frac{w_1}{w_2}=-\frac{3}{5}⇒\frac{w_1}{w_2}=\frac{3}{5}$