30. If $f_V$ and $f_R$ are the focal lengths of a convex lens for violet and red light respectively and $F_V$ and $F_R$ are the focal lengths of concave lens for violet and red light respectively, then we have ?

30. If f_V and f_R are the focal lengths of a convex lens for violet and red light respectively and F_V and F_R are the focal lengths of concave lens for violet and red light respectively, then we have ?

(a) \( f_V < f_R \quad \text{and} \quad F_V > F_R \)

(b) \( f_Y < f_R \quad \text{and} \quad F_V < F_R \)

(c) \( f_V > f_R \quad \text{and} \quad F_V > F_R \)

(d) \( f_V > f_R \quad \text{and} \quad F_V < F_R \)

Answer :  (b) \( f_Y < f_R \quad \text{and} \quad F_V < F_R \)