Arrange the following in increasing order of focal length of convex lens.

(A) $F_v$ focal lengths of voilet
(B) $F_x$ focal lengths of red
(C) $F_b$ focal lengths of blue
(D) $F_y$ focal lengths of yellow

Choose the correct answer from the options given below:

(A), (C), (D), (B)

The correct answer is Option (2) → (A), (C), (D), (B)

Violet ($F_v$) has the shortest wavelength, so its focal length will be shortest.

Blur ($F_b$) has the wavelength after violet, so it's focal length is longer than $F_B$.

Yellow $(F_y)$ comes after blue, so its focal length will be longer than that of blue.

Red $(F_x)$ has the longest wavelength, so its focal length will be longest.