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 a concave lens for voilet and red light respectively, then we must have

f_{V} > f_{R}

and

F_{V} > F_{R}

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f_{V} < f_{R}

and

F_{V} > F_{R}

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f_{V} > f_{R}

and

F_{V} < F_{R}

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f_{V} < f_{R}

and

F_{V} < F_{R}

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Solution

The correct option is B $f_{V} < f_{R}$ and $F_{V} > F_{R}$
Refractive index of a medium wrt violet light is more than wrt red light. So deviation in case of violet ray is more than that of red red ray.
Hence for converging lens ie convex lens a beam of violet parallel rays converges nearer to the lens than the beam of red parallel rays. So $f_{v} < f_{r}$ , as the focal length of convex lens is positive.
For diverging lens ie concave lens a beam of violet parallel rays appears to diverge from more closer point from the lens than the beam of red parallel rays. So $F_{v} > F_{r}$ , as the focal length of concave lens is negative.

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f_{V}

f_{R}

F_{V}

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f_{V}

f_{R}

(f_{r} - f_{v})

(f)

(ω)

f_{r} - f_{v} = ω f

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