If fV and fR are the focal lengths of a convex lens for

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

1. f_V < f_R and F_V > F_R
2. f_V < f_R and F_V < F_R
3. f_V > f_R and F_V > F_R
4. f_V > f_R and F_V < F_R

	1	= (μ - 1)		1	-	1
	f			R₁		R₂

According to Cauchy relation

μ = A +	B	+	C	.... Hence f ∝ λ
	λ²		λ⁴

Hence, red light having maximum wavelength has maximum focal length.
∴ f_v < f_r and also F_v > F_r as focal length is negative for a concave lens.